I don't know whether Schwing mentions guns that low in number. The #39 and #98 guns are in high condition compared to others in the same era I've seen. My non ejector double trigger 21, now gone, was a low four digit number. I like the canoe paddle stock and splinter forend on the early guns for hunting. I have a canoe paddle, splinter forearm gun with single trigger and ejectors. This is a scarce variation only made for a very short time, in my experience and opinion. The ultimate low serial number Model 21 would be #21.