There is a photo on eBay of a 50’ single sheathed double door auto box car number 48921, except I can find no trace of this number being allocated to such a car. The photo is
undated but is post-1958 as it shows the car in the “new” scheme of mineral red with a large “Burlington” spelled out on the side.
https://www.ebay.com/itm/Duplicate-Slide-Freight-CB-Q-Burlington-Route-Friction-Bearing-Wood-50Box-48921/312395272045?hash=item48bc358f6d:g:f5MAAOSwEvZcH0K7:rk:12:pf:0
.
Being a 50’ single sheathed car, it is an XA-14A/B/C (no end doors) which were numbered from 46500 to 46649 and 46750 to 46999. The only group of cars I can find that ever used
number 48921 was allocated to 150 steel XM-33 and XM-33A cars which were rebuilt in 1967 and renumbered to 47575-48924, and this car is certainly not an XM-33!
Rupert Gamlen
Auckland NZ