Security Six Cartouche/Proof Mark?

[AlphaMikeEcho]

Hi there. This is my first post in this forum, thanks for having me!

I have a question about a Security Six that I have in 2 3/4" stainless steel. It's a 1978 production and I noticed today (after having this for almost 10 years) that there looks like there may be a Cartouche/Proof Mark of some kind on the left side of the barrel. Does anyone have any insight as to what this may be?

[RoninPA]

That is the standard Ruger proof mark. It's on all my Six series revolvers, GP100s, Redhawks and SP101s.

Don't know if it is also on the single action revolvers, I have a couple and didn't see it unless it is under the ejector rod housing.

[AlphaMikeEcho]

Thank you! I never really noticed it until recently.

I may need better glasses!