[Edward Tinker]

This is a quote from our book, Simson Lugers, it speaks of the eagle RC after this part (seen on Simson lugers)

RC Stamping

The RC was a common stamp primarily seen on Erfurt Lugers. Crown/RC (in the Imperial era), is the stamp of the Revisions-Commission, certifying an out-of-tolerance part, which was still acceptable for use.
During WW1, the Revisions-Commission was an inspection office in the DWM and Erfurt manufacturing plant. P-08â??s were inspected constantly during their manufacture by inspectors assigned by the Spandau government arsenal. The inspectors' stamps seen often on Erfurt pistols, less so seen on DWM guns, were the inspector's personal guarantee that the part met the applicable standard.

Occasionally a part would be out of tolerance in some fashion, not badly enough to be rejected but questionable--a size or fit problem, hardness of some non-critical part, etc. These parts would be taken before the Revisions-Commission, which would determine the part's "go/no-go" status. Parts that were deemed suitable for use would be stamped by the applicable inspector, and given the crown/RC Revisions-Commission stamp affirming the part's usability. The practical effect of this stamp was to absolve the Inspector of responsibility in case the part subsequently failed in use.

The crown/RC stamp has no relationship to the time of the particular gun's production. It has nothing to do with reissue or rework. It could be said that it represents the limit of acceptable construction. It warrants that the pistol so marked is (or was) "safe to shoot" in its year of manufacture, but as in the case of all decades-old firearms one would do well to have it checked out by a knowledgeable gunsmith before firing it.

[Paraphrased from a discussion with Dwight Gruber]