I've seen several FR machines with square plates like this has, and then there is a wood insert that fits into the cutout instead of the more typical T shaped plate. I'm pretty sure I've got one of those wood inserts around somewhere.
I'd also lean more towards this being a 1920's machine instead of a 1912 machine. There is info somewhere about when White started using the "FR" in front of the serial numbers. Addiction -you come to SD and I'll give you one (or two) and you don't even need to trade for it.