Partial S/N Suffix

[Edward Tinker]

Borrowed Dwights words

Mid-1921 the commercial serial# series reached 92000. DWM converted commercial production to the military convention of numbering, four digits with letter suffix. Numbering began with letter suffix i , guns have upright c/N proofs. This is new designation Alphabet Commercial (formerly 1920 Commercial). (Not all sources agree with Still about the changeover beginning at serial# 92000.)

So, what letters are looking like an 'o' from i to q

o
p
q

So, I would say since p was not used and q is questionable - that I agree with the above