revenuecollector,
WRT the remaining Erler catalogs, I have a source in Germany that I use almost exclusively for my German reference materials. He speaks good English, ships quickly, and can usually get what I'm looking for even if he doesn't have it in stock. I'm not affiliated, I've just had good luck with him in the past.
He currently lists on his website the following Erlers which you don't yet have:
Vol 1 -- Deutsches Reich / Bundesrepublik
Vol 3 -- German States (Anhalt to Kurhessen) to 1945
Vol 4 -- German States (Lippe to Württemberg) to 1945
Vol 5 -- Danzig, Memel, Upper Silesia
Vol 13 -- Municipal Revenue Stamps of the Saargebiet
Vol 14 -- Social Insurance Stamps, LVA Provincial issues
Vol 15 -- Social Insurance Stamps from 1 Jan 1923
Vol 16 -- Social Security Stamps: Saargebiet (this one doesn't have the Vol. number on the cover)
Vol 17 -- Freight Stamps, Newspaper Parcel Stamps, Seat Reservation Stamps, Tax Substitute Stamps
Of the numbered volumes, that would just leave the following:
Vol 2 - -German Colonies & Overseas Steamship Lines
Vol 6 -- Saargebiet
Vol 18 -- Municipal Fee Stamps (IIRC, this one's actually 15+ sub-volumes)
If you ask, Werner might be able to get some of these for you. He was able to locate a few for me that weren't specifically listed on his website.
Erler also wrote at least 18 other issues that aren't part of the numbered series. I only have one (Stamps of the NSDAP (Nazi Party) and its Sub-Organizations). The other cover a
variety of topics, some German and some not.
For German-occupied territories, I also use the books by Hans-Dieter Lutz. They're more specialized studies than catalogs, however -- AFAIK, their catalog references are all to Erler. And they're in German, so...
*** Edited by Staff - Link removed. Website must have been hijacked. ***