That same basic valve is on Bradford Whites, Richmonds, GE's, Whirlpools, and probably every other type. Problems with shared gas control valves of this type is something I noted several months ago in another thread... The Unitrol's seem to be sh*t for production quality.
If I put my nose right down on top of the valve I get a faint whiff of the gas. The mercaptan has a pretty low odor threshold and I can't smell it otherwise (passed bubble tests, etc...wouldn't have noticed it without putting my nose nearly on the top of that dial.) This one is a recent replacement. Best guess: they all leak detectably, but to differing degrees.