Yeah. jjinc24’s Potter FA-50 actually has the same date printed on its backplate (which is red like the one on Caleb’s too!), so it might be the date of introduction or when the patent for the FA-50 & FA-52 was either filed or granted (no idea why they would put a date like that on the station itself of all places but yeah).
Just found this topic which features a catalog page for the FA-50 & FA-52 pull stations, as well as another brand name for them: “Alpha-Larm”, which going by the label on the station was a divison of the Hochiki America Corporation at one time (which as I’ve seen is a brand name they also used for their smoke detectors). It also reveals that the only difference between the FA-50 & the FA-52 is the switch: the FA-50 has an SPST (Single Pole Single Throw) N/O (Normally Open) switch, while the FA-52 has a DPST (Double Pole Single Throw) N/O switch. On another note, the description for them really isn’t written that well grammar-wise (though that might be able to be excused since the Hochiki America Corporation is a divison of the Hochiki Corporation of Japan).