I have just acquired a tilt-a-mite with some M3 bulbs. The guide number table on the back only gives old films that I am having trouble pining down the ASA values for these films that make sense with the data. The two films on the table that I was able to find ASA data for are:
Kodacolor-X ISO-80 GN=150 @(1/100s)
Verichrome Pan ISO-125 GN=240 @(1/100s)
The difference is 2/3 of a stop, so If I multiply 2/3*Sqrt(1/2)*GN it does not fit the data on the table. Sqrt(1/2)=.71 which is what you need to multiply to a guide number to account for 1 stop of film speed slower than the guide number. So I am confused. I think it is stupid they didn't put the film speed on the table.