I think this aux. box predates Fuller and Spicer...but not sure. I think it is a variant of the original Brown-Lipe design. I will include the several casting numbers from the box. Maybe these numbers will assist in a positive ID.
shifter cover: 4879
main case: 5075
side cover: 5660
Grigg, I will check with the ATHS and see if they can help with the ID of the aux. box. More pictures will come in a few days.
Alan