BN GP7 1500 was built as the GN 600 in Novemrber of 1950.
The GN 600 was the first of a six unit order of GP7's numbered 600-605, all delivered in the classic Empire Builder orange and green scheme and equipped with steam generators for local passenger service as well as freight service. There is a photo of the GN 600 on page 92 of the Great Northern color Pictorial #1. GN 600 was assigned to Lines East - Dakota Division up to the March 1970 BN merger.
The GN 600 was then assigned to become the BN 1500. I have not been able to find any photos of the 1500 to verify this was ever done. But the 1500-1503 were sold to the FW&D as 700-703 1-15-72.
The 700 was renumbered to FW&D 1670 by 11/72. The GP7 was retired on 5-23-83 and sold to the Iowa Railroad keeping the number 1670. It was later resold to Farm Rail as FMRC #8255 and named Wichita. Here is a photo from rrpicturearchives of the 8255 from 1999 at Clinton, OK, rebuilt to a GP10.
It has since gone to Gavilon Grain at Jamestown, ND as the 8255 and has been painted blue and looking sharp in this photo from 4-28-15.
That is the last bit of info available on the ex-BN 1500.