I have a recipe for a game pie, circa. 1973.
It calls for a "deep pie dish". Searching online for one to buy, I find deep pie dishes with different depths, and breadths.
Typical pie dishes seem to be about 26cm diameter and a depth of 5cm. Others look deeper and narrower. But I'd prefer to start with tradition.
The recipe, btw, has 1.5 lbs of venison, 1/2 lb mushrooms and 2 oz pickled pork.
There doesn't seem to a standard for pie dish sizes. I'm betting they haven't changed much in size since 1973, or since 1900 for that matter. If you look at modern deep pie dishes, they seem to mostly be in the range of 4 to 6 cm deep. For the ingredients you mentioned, a 26 cm diameter by 5 cm deep pie dish should work.
Wolfram Alpha estimates that your mushrooms will take up 560 cm^3. They'll shrink a lot if you cook them first, but we'll go with 560 for now. I couldn't find a density for venison, but it's not that much denser than water. 1.5 lbs. of water takes up 680 cm^3. The pickled pork may add another 60 cm^3. Add those together and you get 1300 cm^3. The ingredients may not be packed with 100% density, so let's bump the volume up by a liberal 50% to 1950 cm^3.
I'll estimate the volume of the pie dish as if it were a cylinder, which should be close enough. A 26 cm diameter cylinder with a height of 5 cm has a volume of 2655 cm^3, which gives you plenty of room.
