Neil, general convention is a total jetting of '06 on a wand which would be ... hold on while I work out the maths.... a pair of '03 jets
If you had more pressure at your disposal I'd suggest you might find it performs better with a pair of '02s in it on a higher pressure, but I'd stick with the standard jetting at 100psi.
The jets currently fitted should have the size/angle on them, you might need to clean them up with de-scaler if they're a bit crusty!
I'd take a punt they say 9503, in which case replace with the same in stainless! Make sure you get the correct thread, either 1/4" or 1/8" (I'd guess they'd be 1/4" on a standard twin jet)