Most grounds in this country have a large abacus which is operated by one of the three refs from the preceding squad in ABT, UT and OT.
Quite simple to make, you need a large frame fitted with six horizontal bars. Each bar requires 25 markers that can be rotated on the bar. They should be painted, say white on one side and red on the other to signify either a kill or loss.
I ruddy hate it cos after a line of trap my head is like mushy pees. Job looks easy,turn some pegs around but boy its very easy to fleck it up.
I know one smartie pants who watches all six shooters shoot one target then sets all six markers correctly. I cant remember who's turn to shoot let alone who hit and who missed.
The Progrettis are not cheap unfortunately. Best I could find is about £7500 for an 098. There are not a lot of scoreboards going used as people tend to fit them and leave them in place permanently. I've asked about and no one is aware of any up for grabs presently.