Here is a MTH 20-2151-1 O Gauge Santa Fe F3 AA Diesel Engine Set w/PS1 #20/21 . These engines are scale length and feature ProtoSound 1, protocouplers, lights, dual motors in the powered unit, and great detail. Other features include plastic construction, die-cast trucks, knuckle couplers and metal wheels & axles. The pair measures 26 inches long and will run on O-31 track. Please see my photos for a full list of all the features of these Locomotives.
This locomotive does not include DCS (Digital Command System) features because it has ProtoSound 1.0. Only locomotives with ProtoSound 2.0 and ProtoSound 3.0 include DCS functions.

This item has been graded per TCA standards C-6: Very Good based on visual appearance. The wheels show signs of wear. The overall appearance of this item may be improved with a gentle and thorough cleaning. There are light nicks and scratches on the surface of this item. The instruction manual is included. The original box is included. The previous owner has placed stickers on this item’s packaging. Overall condition is Very Good.

Condition: Very Good (C-6)
Operational Status: As is
Original Box: Yes (P-6)

Manufacturer: MTH
Model Number: 20-2151-1
Road Name: Atchison Topeka Santa Fe (ATSF)

Scale/Era: O Modern
Model Type: Diesel Loco

The SKU for this item is 5962490.

Product Id: 11407729