One of mine is ~20yo and another is ~30yo and yes, both seem to expose properly, even with Kodachrome, in the real world.
I recently recalibrated the QL17 GIII so I could use 1600 film. For a while I was obsessing over using something as a standard, other than comparing it with the 20yo Pentax and adjusting so they agreed.
On one hand, I would feel a bit more warm and fuzzy if I could compare these with some kind of a known standard.
On the other hand, the recalibrated camera passes the sanity checks of test rolls, both using 200 film in everyday conditions and 1600 film in dim light.
Oh well ...