The oil can came with a bracket that mounted to the firewall on the bolted "seam" where the two halves of the firewall came together, using one of the firewall bolts. Remember, this oil can (and this bracket) only came on the cars built in the first halve of 1928; later cars would not have come with this oil can or bracket. This bracket had a spring loaded two-part bottom with grasping tabs that held the bottom ridge of the oil can in place.
I'll closely inspect my two original brackets for a manufacturer's mark/stamp the next time I brave the cold and snow to get to my car barn.
The reason we still have a 'Judging Standards Committee', is that there is still much to learn about the Model A and it's parts, pieces, and production. Perhaps sometime 'down the road' this unique oil can bracket may have it's FORD antecedents revealed. Or, it may turn out to be a 'Western Auto' (etc.) product; although none of my products catalogs of the era (1920's through the 1930's) shows it.