You can also just download a tuning app and check for yourself. You probably have to remove the grille to select the M voices separately to measure each one. You should check a few notes around A4 (maybe G4, G#4, A4, A#4 and B4) and average the measurements of the tremolo M reed to find out what the tremolo must have been originally.
I often heard that in the US A4 = 440Hz is pretty standard, but I also often heard from American tuners that they find everything between 440 and 444Hz, so don't take the standard for granted. Around here (Europe) there is no standard. I believe Bugari uses 440 by default (but I have done tuning on Bugari accordions that were 442 and even found one that was 444) and Pigini and Victoria are certainly 442 by default. (Borsini was also 442 by default but no longer exists.)
So don't make any assumptions and just measure.