Hopkinson age estimate

[trevorcoultart]

I've seen a few conversations on here aging Hopkinson Pianos. I have (and love!) a Hopkinson which I bought about 25 years ago. From just the look of the cabinet I'd estimate 1930s but it would be nice to have a better idea.

I've seen that chart of serial numbers - but so far I can't find a serial number on mine. The only distinct code I've found is stamped on the top of one of the side panels and that doesn't fit the format.

Pictures attached for reference, but if there should be a serial number somehwere, where should I be looking?