Hi-- You lost me in a lot of it, but here goes --- Skip the filmless check, since the reading off the black pressure plate is meaningless (I usually put a scrap of film in the camera for TTL-flash meter checks). With GN60 for ASA 100,
that should be about GN42 for ASA 50, so 6' at full power should give you about
f8 minus 1/3, and TTL can't give you any more, of course, so should show
underexposure at smaller stops. If the meter itself is shiny, hold it at a
slight angle when testing so the reflection doesn't affect the reading. If
all is well-calibrated and working right, with 50 ASA set on the flash meter,
in Manual mode you should get f8 minus 1/3 stop; in A mode, you should get
whatever stop(s) the flash shows for ASA 50 (unless it calls for f8 or smaller, or unless the rest of the surface the matte board is on is lighter or darker
than the board - the A flash cell is probably wide-angle and will include much more than the board; and in TTL, there should be agreement with the aperture
set on the lens at one ASA (the series you got is nearly a set of equivalents, indicating no change with aperture?). If the manual and auto checks out,
the TTL should also, unless it just doesn't work. If the M checks, but not the
A, you probably will not be able to check the TTL reliably with that meter,
though TTL may still be working well at some ASA. Let me know what, er,
develops...... David Ruether