The Purdey first patent thumbhole was the original operationg lever for the Purdey bolt, the second pattern was abit neater but then it got overtaken by the invention of the Scott Spindle, which enabled the Purdey bolt to be operated by a top-lever.

The thumb-hole lever guns are elegant but the market currently dictates that they fetch less money than top-lever or side-lever guns.

I would certainly use one - But I have been using a Jones underlever hammer gun all season on driven pheasants and partridges - I still put a good share of birds in the bag and don't think I lose much shooting because of the slower loading cycle.