Hi Mark ,Thats a nice catch! 90,s on I,d hazard a guess,like you have said . I think these true SF cut versions are worth getting your,e hands on now ,quite a few seem to have come out via the SFSG in the last few years .The tape on buttons started mid 90,s if my memory serves me well . They wer,nt too well applied and threads either pulled lose or wore through.
cheers Ollie