Roundhouse/MDC Procor UNPX No. 121030 FMC Covered Hopper
A long, clean-lined industrial freight car representing the specialized covered hoppers that moved dry bulk commodities across North American rail networks.
This assembled HO-scale model is decorated for Procor and carries the reporting marks:
UNPX 121030
The light-gray body is finished with blue lettering, finely printed capacity data, an FMC builder emblem and a printed BLT 10-73 date. It rides on black trucks with metal wheels and retains traditional horn-hook couplers.
The exact road number and decoration correspond with the Roundhouse/MDC No. 3535 FMC covered-hopper release.
Model Details
Roundhouse/MDC No. 3535 identification
Procor leasing-company decoration
Reporting marks UNPX
Road number 121030
FMC three-bay covered-hopper body
HO scale, approximately 1:87
Light-gray body with blue lettering
Metal wheels
Black trucks
Horn-hook/X2F-style couplers
Long roof trough hatch
Roofwalk and end platforms
Three discharge bays
Brake wheel and end ladders
Assembled and ready for buyer inspection
Choo Choo Boys SKU 011840
The FMC 4700 Covered Hopper
The model represents the general form of an FMC 4700-cubic-foot covered hopper.
Covered hoppers protect dry bulk freight from rain, snow and contamination while allowing the load to move by gravity through outlets beneath the car. Unlike an open coal hopper, the roof and loading hatches keep the cargo enclosed throughout its journey.
The long raised hatch running along the roof allowed the prototype car to be loaded from overhead equipment. Beneath the body, three sloped hopper sections directed the cargo toward separate discharge outlets.
That design was useful for commodities that needed protection while still benefiting from efficient gravity unloading.
Understanding the Printed Capacity
The model carries a capacity marking of approximately:
C.U.M. 133
That indicates roughly 133 cubic meters of internal volume—close to 4,700 cubic feet.
The printed data helps explain the car’s long, high-sided form. A covered hopper must create substantial internal volume while staying within railroad clearance and weight limits.
The body’s broad side panels, long roof hatch and three discharge bays all reflect that practical freight-car mission.
Procor and Private Freight Cars
Procor is associated with the leasing and servicing of specialized railroad equipment.
A leased car allows a shipper to obtain equipment designed for a particular commodity without relying entirely on whatever freight cars a railroad happens to have available.
The reporting marks end in X, a convention used for privately owned or leased cars rather than cars owned directly by a railroad.
That makes this model useful in mixed freight trains behind many different North American locomotives. A privately leased hopper could travel over several railroads during the course of one shipment.
The UNPX Reporting Mark
The car is lettered:
UNPX 121030
The reporting mark and number function as the freight car’s identity.
Railroads used that identification to track:
Ownership or leasing responsibility
Car movements
Interchange activity
Maintenance records
Loading and unloading
Mileage and billing
Empty-car return instructions
On a model railroad, reporting marks give a freight car its individual identity even when several cars share the same basic color and body style.
Built-Date Appearance
The printed BLT 10-73 marking represents a prototype build date of October 1973.
That places the represented freight car naturally within layouts depicting:
The 1970s
The 1980s
The 1990s
Later eras with an older car still in service
Canadian and United States freight operations
Industrial switching
Grain and dry-bulk terminals
Mainline manifest trains
Unit or block hopper movements
The model is not being sold as a newly manufactured 1973 item. The marking represents the prototype freight car, not necessarily the production date of the miniature.
Roundhouse/MDC Kit Heritage
Roundhouse and Model Die Casting produced freight-car kits for hobbyists who enjoyed assembling, detailing and upgrading their own rolling stock.
Kit-built cars can vary because the original owner controlled:
Assembly quality
Adhesive use
Wheel selection
Coupler selection
Added weight
Detail alignment
Weathering
Paint touch-up
Final adjustment
This example appears to have been assembled from the known Procor kit and later fitted with metal wheels.
That upgrade can offer several advantages over lightweight plastic wheels:
Additional low-mounted weight
More realistic appearance
Cleaner wheel treads
Improved electrical detection on equipped layouts
Better long-term rolling potential
Reduced plastic buildup on the tread
Actual rolling quality still depends on axle length, truck condition, wheel gauge and track condition.
Kadee Couplers Upgrade
These were once standard equipment on many HO-scale train sets and kits. They remain usable with compatible rolling stock but do not directly couple with modern knuckle-style couplers unless another car or adapter provides the transition.
Before operating, check:
Coupler height
Coupler centering
Coupler mounting
Truck swing
Wheel gauge
Free rolling
Car weight
Minimum curve clearance
Layout Uses
This Procor hopper can work naturally in several operating settings:
Industrial switching layout
Canadian freight train
Cross-border manifest freight
Covered-hopper block
Grain or bulk-material terminal
Railroad interchange scene
1970s freight consist
1980s or 1990s layout
Modern-era train with older equipment
Car-leasing-company collection
Its neutral gray body also creates a useful contrast with colorful railroad-owned boxcars, tank cars and locomotives.
Fine Freight-Car Details
Visible molded details include:
Vertical side ribs
Capacity and weight lettering
Long roof trough hatch
Roofwalk
End platforms
End ladders
Brake wheel
Open end framing
Three hopper bays
Discharge-gate detail
Black trucks
Metal wheels
Couplers at both ends
The printed lettering remains one of the model’s strongest features. The large blue Procor name is easy to read from normal layout distance, while the smaller data rewards closer inspection.
What You’re Buying
You are purchasing:
One assembled HO-scale covered hopper
Roundhouse/MDC No. 3535 attribution
Procor decoration
UNPX road number 121030
FMC three-bay covered-hopper body
Metal wheels
Horn-hook couplers
The exact model shown
Choo Choo Boys SKU 011840
Not Included
Original box
Instructions
Unused kit parts
Replacement couplers
Additional wheels
Track
Locomotive
Other freight cars
Display stand
NMRA gauge
Original paperwork
Any accessory not specifically shown
Detailed Condition
This is a previously assembled and used model-railroad freight car.
The body shows light scratches, dust, small stains, discoloration, handling marks and minor paint or lettering wear. Small marks are visible along portions of the roof, lower edges and end areas.
The roofwalk, hatch, ladders, end framing and brake-wheel components appear present in the photographs. Fine details may show slight bends, uneven alignment, adhesive residue or earlier assembly adjustments.
The trucks and metal wheels show age and surface wear. Wheel gauge and free-rolling performance have not been measured.
Both horn-hook couplers remain present. Their height, centering, spring action and compatibility with the buyer’s equipment have not been tested. One or both may require adjustment before reliable operation.
The model has not been track-tested by Choo Choo Boys. No guarantee is made concerning rolling resistance, derailment performance, minimum curve operation or coupler function.
Please review all photographs carefully. They are the primary condition reference and show the exact lettering, roof, ends, underside, trucks, wheels and couplers.
Professionally packed & shipped with care — keeping classic trains rolling, preserving the stories, and Protecting the fun every step of the way.
ITEM SPECIFICS
Brand: Roundhouse / Model Die Casting
Manufacturer: MDC Roundhouse
Catalog Number: 3535
Model: FMC 4700 Covered Hopper
Type: Three-Bay Covered Hopper
Corporate Roadname: Procor
Reporting Mark: UNPX
Road Number: 121030
Printed Build Date: 10-73
Gauge: HO
Scale: 1:87
Rail System: Two-Rail
Power Type: Unpowered
Control System: Not Applicable
Assembly Status: Assembled / Pre-Built From Kit
Material: Plastic Body with Metal Wheels
Color: Light Gray / Blue / Black
Wheel Material: Metal
Coupler Type: Horn-Hook / X2F Style
Number of Bays: 3
Roof Type: Continuous Trough Hatch
Theme: Freight / Railcar Leasing / Industrial Transportation
Original Packaging: No
Vintage: Yes
Exact Model Production Year: Unknown
Condition: Used
Choo Choo Boys SKU: 011840
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Assembled Roundhouse/MDC No. 3535 HO-scale Procor UNPX 121030 FMC three-bay covered hopper with light-gray body, blue lettering, metal wheels and horn-hook couplers.
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