Erfurt with "M" marking

[mrerick]

Today, a friend showed me the Erfurt "1918" date Luger that his father brought back from WW-II Germany.

It has been in the family since his return.

It's all matching with some unusual characteristics. Has anyone seen these before?

• There is a capital serif "M" stamped on the left side of the frame above the trigger and covered by the trigger plate. There is also a similar "M" stamped on the top of the trigger itself.
• There is a E/6 (Simson) marked rear toggle
• There is a unusual Nazi era Eagle over a three letter sequence on the right side of the receiver behind the normal location of acceptance and proof stamps
• There is only one Crown over letter acceptance stamp. There are four Crown/RC stamps, with one above the Crown over letter acceptance
• The gun is in high condition with all numbered parts correctly matching including the E/6 rear toggle
• The rear axle pin is not numbered
• The barrel is staked and appears original to the receiver with continuous witness mark

I assume that this was a Simson rework of an Erfurt. It could also be a depot rework using parts sourced from Simson. Are these a known variation / rework program?