Here's a list I keep.
As shown, the pre-Blocks stretch as far back as 10 57 and the Blocks as late as OCT 9 1975.
In 1987 I bought this plastic bodied variable 1/3-HP m-257.190470 CM non-Block grinder.
Note: The wheel guard and covers are shown removed for photo purposes. Never operate a grinder without full wheel guards, covers, and associated hardware in place and properly adjusted.
I'm not sure of the COO, sorry.