From the website https://utahrails.net/drgw/rg-diesels-4.php on D&RGW Diesel Locomotive Roster, under EMD F7B, may be the one:
5712 | Jun 1952 | 16533 | 22 Feb 1970 | Sold to Penn Central, 28 February 1970; in service as PC 712; renumbered to PC 3479; renumbered to Conrail 3873; retired on 24 May 1978; traded by CR to EMD. |