[CR]Campy NR 'PATENT' rear derailleur date?

CR Folk:

I've seen many NR rear derailleurs that had an inscription like "PAT. 78" on the pivot-bolt housing.

But now I've got one that just has the full word "PATENT" spelled out. What year would that be?

I consulted the Campy timeline, but didn't see any reference to this sort of thing.

Brad Stockwell
Palo Alto