The 2000 FC was the first with the bigger mirror, back in 1977. All later 2000-series models have it as well.
Next in line to get the bigger mirror was the 500 ELX in 1984. Again, all later EL(...)-line models have the bigger mirror.
The 503 CW was the first in the C-line that got the bigger mirror, in 1996.
Though already 19 years after it first appeared in the 2000 FC, 12 years after the EL(...)-models got it too, it was presented as if it was a new feature when the 503 CW appeared.
Yet it and the 501 CM which appeared one year later were not the first, but the last in line to get it.
In the C-line only the 503 CW and 501 CM have it.
When looking for a 501, don't confuse the 501 CM with the 501 C (no "M"). The 501 C does not have the larger mirror.
Acute Matte screens was one of the changes (one other was Palpas internal coating) that made the 3rd generation, so were introduced in the 503 CX, 553 ELX and 2003 FCW in 1988.
Since screens are freely interchangeable, many earlier cameras have an Acute Matte screen inside, while there is no guarantee that 3rd generation and later bodies do not have an older screen. So make sure when buying used.