"as game as they make them"?
"Oh, I suppose she was after your time. She\'s the mater\'s factotum, companion, Jack of all trades! A great sport--old Evie! Not precisely young and beautiful, but as game as they make them."
from The Mysterious Affairs at Styles by Agatha Christie

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Still in use today - "Who's up for some/a [fun action]?" To which one can answer, "I'm game." I'm ready/willing. :)

Answer

This is an old-fashioned way of speaking.  "game" as an adjective refers to someone who is ready for fun, adventurous, vivacious, and willing to get involved in new things.

"they make them" refers to whoever creates human beings!  So Evie is one of the gamest people ever created and put on this earth.

Answer

It is an older expression, and slightly cheeky.

It means she is as [likely to engage in games / fun] as [any person you could hope to meet].

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