Students’ calcs in the 70s/80s

[Leviset]

Don’t know if anyone can help with this?
I studied Pure Mathematics between 1980 - 1984 at University, the course included a 1 year Computer Science component.
My 1980s calculator was a Casio programmable - bought for me by my Father in Law!
It was step programmable and I think it was on of the Casio FX- models.
All I can remember is that it had a [PRG] button and 4 storage areas on 2 keys giving [P1], [P2], and inverse of those 2 gave [P3] and [P4] locations.
I can’t find the model - I’ve looked really hard honestly!
He bought it in 1980/81 and I think it was possibly one of the FX-80/81/82 range
Dennis