I don't know about your instrument.
I do know how instrument manufacturers generally operate.
The manufacturer makes an instrument and markets it.
Later, they find ways to make slight improvements in the original instrument.
Not enough improvements to create a new instrument number, just enough to make the
original instrument better. Maybe a couple added features, maybe better circuit function.
Though I can't swear to it, I'd bet good money your 2955A has slightly better specs
than the 2955.
If you Google the spec sheets on the two instruments, that's probably where you'll
find the difference(s) that you're wondering about.
