Slightly unusual 3278 beamspring

[mathdude3]

I recently bought and began restoring an IBM 3278 beamspring board and I noticed couple odd minor differences between my 3278 and other examples I've seen online. The foam is white rather than black, it doesn’t have the IBM Canada 1977 text on the back, and it has these two divots in the back plate I haven’t seen elsewhere. Not pictured, but one of the screws holding the main assembly with the switches together also had a nut on it. Anyone know where or when this one might have been manufactured? I couldn't find a date stamp or a country of origin stamped anywhere on it, but it's possible I just missed it.

Pictures are too big to attach, so here's an imgur link to them: https://imgur.com/a/zvRjAGW