The LP says A1 and B3 what does this mean

I have a Pink Floyd LP WYWH
and the it says A1 on side 1 and B3 on side 2 , does anyone know what that means. This is stamped on the wax part of the LP , made in the UK
probably first press of side one, third press of side two...
Does the A1 side sound better?
Are you sure a disc isn't missing? I have severalSalbums that are pressed with Side 1 and Side 3 on one LP and sides 2 & 4 on the second LP so you can cue up the second side and mix with no interruption. This goes for rock records not DJ/Techno albums.
There were 13 sets of stamper codes for the first release of WYWH in the UK.

Yours is a very early pressing and depending on the series of letters and numbers after A1 and B3 could be anywhere between the 1st and 7th pressing.

Hang on to it.
Here ya go dude, everything you ever wanted to know about Floyd pressings:

BTW the bootleg, "Screaming Abcabs" is a must own.