Hi RAC,
From the 24th. edition of the Blue Book of Gun Values (the 25th. edition is now out...so the prices below might be a bit low...) :
M1900 Commerical DWM Luger in 7,65 cal. :
$ 3000 USD at 98% orginal finish
$ 2500 USD at 95%
$ 2000 USD at 90%
$ 1650 USD at 80%
$ 1325 USD at 70%
$ 950 USD at 60%
It is a bit difficult to tell from your photos, but my guess would be yours is in the 80-85% finish range...
In Jan C. Still's book on Imperial Lugers on page 11, a table reports serial numbers in the 50-19294 range; with an estimated 5,750 made. Your number 16220 seems to be in the later period of the production.
Regards,
Pete... <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />