Hi Cathy,
A wonderful collection of Boye cabinets. The old style numbering cases don't seem to be very common. I think this Boye fellow was a marketing genius even with the wacky dual numbering system. Sort of adds to the interest.
I bought a Boye cabinet similar to yours with the wood base but with the newer system numbering. It has both 2-1/2 and 20-1/2 spots on the tin. Hopefully it arrives safely from your neck of the woods, South Dakota.
Jon