http://cgi.ebay.com/Vintage-Luger-Nu...QQcmdZViewItem
laoshi75,
I think the W is more likely to be a worker's mark than anything to do with the number.
The number itself does not look like standard WWI serial number grip stamping which I am familiar with. They will not suffice as a proper "force match" for your Erfurt because there are no Army inspector stamps (c/letter).
Whether or not they will fit is a good question and only to be determined by the actual attempt.
--Dwight