What are all those numbers and letters at the end of classical music titles?

Let's have an explore...

If you wish to buy me a coffee, that would be appreciated:
https://www.buymeacoffee.com/classicalmk
__________________________________
Beethoven Pastoral: Sir Adrian Boult with the BBC Symphony Orchestra recorded August 1, 1972, the Royal Albert Hall.

The Sad music is of course Elgar's Cello Concerto: https://www.youtube.com/watch?v=7rVW4

Haydn London Op 104    • Haydn  Symphony No. 104  London (Pr...