Before watching the movie:
This is clearly a cash-in on the Indiana Jones franchise, but it’s a response to a pulp adventure pastiche with one of the original pulp adventurers. I don’t know much of anything about Allan Quatermain (I’m discounting everything I might remember from League of Extraordinary Gentlemen because it’s a bouillabaisse of literary big names with little regard for detail) other than that he’s the inspiration for a lot of more recent adventure throwbacks.
I guess I saw him in The Three Musketeers, but I don’t really have a very strong impression of Richard Chamberlain yet. I have a hard time keeping the Musketeers that aren’t D’artagnan straight.