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GIBSON OPEN-BOBBIN HUMBUCKER, BELIEVED '57 CLASSIC PLUS
CONDITION
I identify this as a used Gibson open-bobbin humbucker. Based mainly on its measured DCR of 8.547 kΩ, I believe it is most likely a '57 Classic Plus. However, no complete model designation survives on the pickup, and DCR alone cannot establish the exact model or winding history. I therefore do not present the '57 Classic Plus identification as confirmed. A rewound '57 Classic, or another altered Gibson pickup with similar measurements, cannot be completely excluded.
I confirmed DC continuity and obtained the stable DER EE DE-5000 readings shown below. My REW impedance measurement also shows a clear unloaded electrical self-resonance. I do not describe this as a complete amplified-audio or magnetically excited output-response test.
When I acquired the pickup, it had a large amount of wax attached to it. I lightly cleaned away some of the excess wax. In my judgment, the amount and distribution of the wax suggest that the pickup may have been re-potted, but I cannot confirm when, by whom, or exactly what work was performed.
The baseplate appears bowed or distorted around the pole-piece area. Together with the wax condition and visible construction, this raises the possibility of prior disassembly or other internal work. I do not claim that the pickup remains factory-sealed or factory-original internally.
The black bobbins, nickel-plated pole pieces, baseplate, braided lead, tape, and remaining label show scratches, scuffs, wear, residue, oxidation, discoloration, and other signs of use. The black label on the baseplate is heavily damaged and incomplete. Please examine all photographs carefully.
The braided lead is short, measuring only approximately 13 cm / 5.12 in to the end of the braid. I include the pictured used slotted mounting screws and new springs.
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I identify the pickup as Gibson from its construction, baseplate, single-conductor braided-shield lead, black bobbins, and the surviving portions of its black baseplate label. The exact factory model marking is no longer legible.
The measured 8.547 kΩ DCR led me to judge that a '57 Classic Plus is the most likely model attribution. That reading is compatible with a somewhat hotter PAF-inspired Gibson bridge humbucker, but it is not a unique model identifier. A pickup can also reach a similar DCR through production variation, temperature, repair, or rewinding.
Because the physical condition suggests possible prior work, I specifically leave open the possibility that this could be a rewound '57 Classic or another modified Gibson humbucker. I state the '57 Classic Plus attribution as my informed judgment, not as a confirmed factory specification.
| Manufacturer identification | Gibson |
| Model attribution | Believed to be '57 Classic Plus, based mainly on DCR; exact model unconfirmed |
| Alternative possibility | A rewound '57 Classic or another altered Gibson humbucker cannot be excluded |
| Construction | Open black bobbins; nickel-plated pole pieces; single-conductor braided-shield lead |
| Possible prior work | Possible re-potting and disassembly; not independently confirmed |
| Included hardware | Pictured used slotted mounting screws and new springs |
I measured DCR, series-equivalent inductance, and Q with a DER EE DE-5000 LCR meter. I report the meter readings directly and do not apply temperature normalization.
| Measurement | Result |
|---|---|
| DCR | 8.547 kΩ at 25.5°C / 77.9°F |
| Relative humidity | 57% |
| 100 Hz Ls / Q | 5.006 H / 0.366 |
| 1 kHz Ls / Q | 4.759 H / 2.36 |
| Approx. unloaded electrical self-resonance | 8.01 kHz |
| Peak impedance at resonance | Approximately 521.8 kΩ |
| REW graph marker phase | -9.1° at the selected resonance marker |
| Lead length | Approximately 13 cm / 5.12 in to the end of the braided shield |
| Pole spacing | 49.2 mm / 1.94 in |
| Pole-surface magnetic averages | Adjustable screws: 30.34 mT / 303.4 gauss Slug poles: 31.87 mT / 318.7 gauss |
| Electrical phase | Matched the Gibson electrical convention in my comparative check |
I measured the unloaded electrical impedance behavior with REW V5.40 Beta 132 through a Yamaha AG06 at 48 kHz/24-bit, using Rsense 100.00 kΩ and Rref 100.00 kΩ. The measurement shows a clear unloaded electrical self-resonance at approximately 8.01 kHz, with peak impedance of approximately 521.8 kΩ.
This is an unloaded electrical impedance self-resonance. It is not a peak from a magnetically excited pickup-output frequency-response test. The 521.8 kΩ figure is peak impedance at resonance, not an output level and not a dB value. I have not measured magnetically excited output response or peak output dB for this pickup.
The -9.1° figure is the phase value at the selected REW impedance-graph marker. It is not the same measurement as the Gibson-relative electrical phase comparison described below. Likewise, the DE-5000 Q readings of 0.366 at 100 Hz and 2.36 at 1 kHz are not measurements of resonant Q at 8.01 kHz.
The measurements confirm DC continuity and a clear unloaded electrical resonance. Installed behavior will change with volume and tone controls, cable capacitance, switching, and the input impedance of connected equipment.
I found considerably more wax on the pickup than I would normally expect from light factory residue. I removed some loose and excessive surface wax to make the construction easier to inspect, but wax remains around the coils, tape, and baseplate.
I consider re-potting a reasonable interpretation of the wax condition, but I do not present it as confirmed. The bowed appearance of the baseplate around the pole-piece area also suggests that the pickup may previously have been disassembled, adjusted, repaired, or otherwise worked on. I cannot reconstruct its complete service history from appearance alone.
These observations are also why I cannot eliminate the possibility of a rewind. I have not unwound the coils or performed any destructive inspection, so I do not claim confirmation of the wire gauge, insulation type, turn count, or originality of the winding.
I took the magnetic readings with a digital teslameter and averaged the absolute surface readings from all six adjustable screws and all six slug poles. The adjustable-screw average was 30.34 mT / 303.4 gauss, while the slug-pole average was 31.87 mT / 318.7 gauss.
I treat these as comparative pole-surface measurements. I do not interpret them as direct measurements of total magnet strength, magnet alloy, grade, remanence, coercivity, or maximum energy product. Pole height, sensor placement, magnet charge, and the surrounding magnetic circuit can all influence the readings.
My comparative electrical phase check matched the standard Gibson electrical convention. The REW graph-marker phase is a separate impedance measurement and should not be confused with this wiring-polarity comparison.
Based on the 8.547 kΩ DCR and 5.006 H series-equivalent inductance at 100 Hz, I would expect a moderately strong vintage-style humbucker response rather than an extreme modern high-output design. Under otherwise comparable loading, these values suggest somewhat more winding and midrange weight than a lower-DCR, lower-inductance PAF-style pickup.
I cannot determine exact sound or output level from these measurements. Audible results also depend on distributed coil capacitance, installed resonant frequency, winding geometry, magnet material and charge, pole adjustment, pickup height, strings, control values, cable capacitance, guitar construction, amplifier, and playing technique. Any prior rewinding or re-potting could also influence the result.
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The business operating this store has independently placed on the public record its support for evidence-based, product-specific treatment of musical instruments and parts under HTSUS Chapter 92. This statement reflects the seller’s own views and does not imply endorsement by eBay or any manufacturer.
This item is not drop-shipped. I personally own, photograph, inspect, pack, and ship everything I sell.
What you see is exactly what you will receive. I do not use stock images or third-party fulfillment.
I have been an eBay member since 2004 and have more than 30 years of experience with vintage guitars and parts.
To the USA: I ship via Japan Post or eBay SpeedPAK with full tracking. For qualifying merchandise shipments under current U.S. postal-import rules, I prepay the applicable import duty through the required DDP procedure. In other words, the applicable tariff is already covered, so you should not receive an unexpected import-duty bill at delivery. eBay may still collect state sales tax at checkout, and separate carrier or customs-processing fees may apply in some cases.
To all other countries: I ship from Japan with tracking. Import VAT, customs duties, clearance fees, and compliance with local import regulations are the buyer's responsibility unless collected at checkout.
I accept returns within 30 days. The buyer is responsible for return shipping when the return is based on preference, compatibility, phase relationship, or another buyer-related reason.
I handle all returns in accordance with eBay policy. Cutting or extending the short lead, soldering, installation, disassembly, re-potting, changing a magnet, rewinding, or any other modification changes the item's condition and may affect return eligibility or the refund amount to the extent permitted by eBay policy. This does not limit the buyer's rights if the item is not as described.
This vintage product may contain lead, nickel, or other substances known to the State of California to cause cancer, birth defects, or other reproductive harm. Wash hands after handling and avoid unnecessary exposure.
I consider this a used Gibson open-bobbin humbucker most likely attributable to the '57 Classic Plus model from its measured DCR, while fully disclosing the short lead, damaged label, wax condition, bowed baseplate, and unresolved possibility of prior re-potting, disassembly, or rewinding.
I am not affiliated with or endorsed by Gibson Brands, Inc. or any other manufacturer. I use brand and model names only for identification and descriptive purposes. I state the '57 Classic Plus attribution, possible alternative identification, prior-work discussion, electrical interpretation, and magnetic interpretation with their respective supporting evidence and limitations.