Commercial with 3 digit serial number
 

I purchased my first luger about a year ago at a local gun show. It was sold as a 1920 commercial with original finish. I paid too much for it, but it was an impulse buy rather than a rational decision. Now that I'm becoming more interested in collecting lugers I noticed that it has a 3 digit serial number stamped on the barrel and the front of the gun right under the barrel (sorry for not knowing the correct term) and the last 2 digits of the serial number stamped over the rest of the gun. Is this low serial number normal for a 1920 commerical? In looking on gunbroker/auctionarms/simsonltd I have not seen another. Pictures available on request.