Rob P - excerpt taken from ‘Henry VII Groat Without Mintmark’ thread
“Guaranteed to be a lot of dies.
Potter & Winstanley note 16 obverse dies for no mark, lis and Greyhound's Head, but give up when it comes to Cross Crosslet. For what it is worth, they list 7 dies each for no mark and Lis, plus another 2 for Greyhound's Head. Crosslet is much more common. As far as the reverses go, you can reasonably expect a minimum of twice the number of obverse dies. Greyhound's Head being the rarest and hence the simplest case, the sylloge has an example of dies 15/16 (nearly identical) plus 3 GH reverses from 2 dies including muled marks. Add to that my GH rev. (below) plus another not in the Ashmolean gives a total of 4 GH rev. dies I know for certain. You are unlikely to be looking at more than another one or two reverses, if they do indeed exist.
A back of the fag packet calculation assuming 1:2 obv:rev gives a total of 50 or so rare mark dies for both sides, plus a guesstimate of say 100 crosslets would give a total of 150ish tentative dies for all marks. If someone wants to do the survey, then we can plumb in the numbers and obtain a more precise estimate of the number of dies.”