I have no clue but it doesn't look too old since its the same design as the current ones

Hmm... Looks like an old dot matrix font. Could the "88-48Z558" be the date stamp/batch number?

One thing I know....is the label...the oldest could be 1988-1989.....why? because the GE Logo meatball design on this label is a newer GE meatball which was redesigned in 1988-1989.....(take a very careful look at the 4 curved lines around the circle and the swirl on the "E" in new and old logos!

At least it does correspond what I suspected....

I looked at the M400A2 FCO and its late 80s. The NEMA tag was what GE used during '87-'89 or so. So '88 sounds right.

UPDATE: I looked at the label in the M400A2 and I found the date code. PD which translates into March '89! How did the gull miss that date code? Lolol!

Actually I saw it and told Rych I believed it was 1989 but wasn't too sure....ask Rych...