These are SwitchCraft WMT-332A Audio Jack with smooth 
Long Frame Phone Jack - Mono 1/4 inch Guitar or Speaker Jack
WITH INTERNAL INLINE NORMALLY CLOSED SWITCH
with palladium crossbar switch contacts

The jack may be wired to either interrupt the signal as a bypass, or route the signal to a different path. 

{for those who actually bother reading these eBay listings - I have used two of these jacks to replace factory original cheap plastic in a vintage amp. With solid wire wrapped on pin connections solder is an option, but not needed. The smooth shiny barrel looks better than a chrome nut.}

There were 178 pieces at the time of this listing. These are being sold individually. 

SPECIFICATIONS

Frame and Stack Screws: Plated steel, with iridescent

iridite finish.

Springs: Copper alloy, spring tempered. Solder lugs are tinned.

Bushings: Plated copper alloy standard. Natural brass finish.

Insulation: Rigid plastic spacers (MIL-type PBE-P per

Specification LP-513). One piece molded through stack.

Contacts: Welded crossbar palladium contacts in shunt and isolated switching circuits are standard. 

  • Contact Resistance: 0.03 Ohms
  • Dielectric Withstanding Voltage: 500 Volts
  • Insulation Resistance: 10000 MOhms
  • Circuit-Schematic: Double Open

MECHANICAL

Life: Commercial jacks: 20,000 insertion/withdrawal cycles

Mechanical Shock: Military Jacks – Per MIL-STD-202, method 213, Test Condition H (75g).

  • Body Material: Copper Alloy
  • Insert Material Type: Thermoplastic
  • Terminal Material: Copper Alloy Tinnned
  • Spring Material: Palladium
  • Frame Material: Steel

Vibration: Military Jacks – Per MIL-STD-202, method 213, (10-55 Hz).