Stihl Piston Rings - Made by Elko?

I have my 025 apart that I bought a few weeks ago and pulled the rings out tonight. I noticed they say ELKO on them and they do not say Stihl or have a Stihl logo. Are these the OEM rings for this saw? I'm starting to wonder if this saw has been worked on before and someone put aftermarket rings in it. I did a search on AS and on the internet but didn't find much.