[time-nuts] HP internal part numbers.

[Rex]

I'm trying to figure out the basics of some circuits in my HP Z3816A
timing receiver.

There are two chips in it marked with this HP part number:
1820-5950

They are 14-pin DIP chips and seem to be made by National Semi.

Does anyone have a reference list or link that might cross-reference the
HP part number to a standard part number or description?

From the context of the board, I am guessing they could possibly be PLL
chips. If no one can look up the numbers, can anyone suggest National
PLL chips in 14-pin dip that might have been used by HP around 1996? I
could try some guess work.

Thanks for any help.