The initials are sometimes covered, or all but covered, by the lower rib. I don't recall seeing one, but it looks like a scalloped GECO-Anson receiver. Meffert sometimes sourced tubes from Heinrich Ehrhardt/Rheinische Metallwaaren Maschinenfabrik(RM&M) in Sommerda which was founded in 1889 to take full advantage of Ehrhardt of Dusseldorf patents. By WWI RM&M was second only to Krupp. Due to the Treaty of Versailles, 17cm was the max. diameter to be produced and by 1926 there looks to have been a name change to Rheinmetall AG.
Kind Regards,
Raimey
rse
