Hmm, that's interesting. Mine certainly has a number. I'm baffled now.
This is not likely a serial number. It is in the casting so there are likely others with the same number.
While it is possible to switch parts of the mold for sand casting, it is extra work unless the manufacturer feels each piece requires a separate number in which case most all serial numbers are stamped or engraved.
I have seen a couple older Jensen steam engines with an odd number in the casting.
Gil