A page I found quite good..

[Björn Jervas]

Hello!
As I surfed into a militaria dealer home site today, I found a brief - but good page describing manufactor codes etc. Any comments?
This is it: http://www.german-militaria.co.uk/markings.htm

Björn

[Richard]

A pretty good referece. But I think he is in error on the RS mark for Rudolf Souval. Souval used both the angular and rounded S on his marked badges prior to 1945. The distinquishing characteristic on post versus pre 1945 examples is almost always the catch.
Richard

[Mark S.]

Although I applaud this perrson for his effort, this is merely a rehashing of the information in the back of Fuhrer amd Fatherland, which was copied from "one rather widely circulated listing of L numbers provided by the firm of Steinhaur and Luck of Ludenscheid"

As this book was initially printed 20 odd years ago, new information since then has come to light.

The numbers assigned to those firms listed are Prasidialkanzlei Numbers, or firm numbers. You will notice that they dont correlate with LDO numbers, or numbers prefixed by the L designation.

The Leistungs Gemeinschaft der Deutscher Ordenshersteller numbers (LDO) are numbers assigned to licensed firms, and many firms had both LDO and Prasidialkanzlei numbers assigned to them.

I think you will find that this website has a much more concise listing, plus more up to date information.
http://dev.wehrmacht-awards.com/reserach_tools/ldo.htm