Bud, Stan -- I had purchased two and a half GG1s when they first appeared on the market -- One to run as-is, one to cut up into the loco on the photo plus a boxcab switcher, and a powered chassis sans body, which will become a New Haven EP-3.
My road's classification scheme shows 4-6-4 locos to be Class M. The two electrics I have of that wheel arrangement (2-C-2) are an M-1 boxcab and the pictured M-5a streamlined version. It is fairly close in appearance to the PRR Class P5a. Stan -- That prototype photo you posted sure is an ugly GG1 bash. I'd be embarrassed to have something like that on my NYW&B! Dick Karnes
