For really baked on tinting the only thing I've heard of is a soak in
household ammonia cleaner.  You have to remove the glass and soak really
tough ones for a week. For less difficult situations you might try
spraying it on the window, but do it outside and with all the doors and
windows open.  Lightly score through the material in several places to
help the ammonia solution penetrate.  Use a light touch with a razor
blade to avoid scratching the glass, and keep the ammonia off the paint,
it will remove it too if its allowed to sit!

--
Stuart MacMillan
Seattle

'84 Vanagon Westfalia w/2.1
'65 MGB (Daily driver since 1969)
'74 MGB GT (Restoring sloooowly)

Assisting on Restoration (and spending OPM):
'72 MGB GT (Daughter's)
'64 MGB (Son's)

Stripped and gone but their parts live on:
'68 MGB, '73 MGB, '67 MGB GT