I believe that is the Edison - Beech 1912 Storage Battery Electric Motor Car, #105, originally purchased by the TVRR for runs from Fairbanks to Fox and Chena.  It was later converted to Gas Electric.  

There is a reference, with photo, to a Federal Electric Motorcar in Osborne's  book (Alaska's Tanana Valley Railroads, page 64) and a Brill Motorcar with photo (page 124).  I am not sure of his accuracy.

Tracks to Chena were torn up in 1919, but service to Fox and beyond continued. #105 continued to provide service to the University, probably until the Narrow Gauge Ops ceased in August of 1930.  The track was removed from the Chatanika end, back to Fairbanks, so the Motor car could have been used until the track was no longer there.  I do not know how or when the ARR disposed of it. 

When the widened AEC  tracks reached HAPPY, the narrow gauge tracks remained in place, so that service to Chatanika could continue, and the dual gauge trackage, 11 miles, continued into Fairbanks as the narrow gauge ops continued,  .  The FTVRR/ARR narrow gauge ops ended in August 1930, I believe the date was the 30th.

Deely has a fascinating narrative about the rail widening from Nenana  to Fairbanks, beginning on page 131. I hope this info is helpful!

- Dan Gullickson