"Late" vs. "Early" HP-34C's?

[Karl W. Schneider]

Spice gurus --

Would anyone know when the changeover occurred (in terms of date or serial #) between "early" HP-34C's with pressed-in chips and display leads vs. "late" units with soldered-in components?

All the recent auctions seem to be early units from 1981 or earlier. I would suspect that sales HP-34C's dropped off precipitously following the 1982 introduction of the 15C; the 34C was discontinued in 1983. (Interestingly, new, probably-leftover 34C's were still available in November 1983, when I bought my 15C after comparing it side-by-side with the 34C.)

Thanks.