So I just replaced my first closet flange. It was some sort of cast metal 3" offset flange (surprise) from the 60's, and I needed to convert back to a regular flange for a 10" rough to accomodate a Toto.

I assumed it was cast iron, and began the process of drilling out the lead, etc. Then reality set it - no lead ring, no oakum. A tinge of green on the inner wall of the pipe. Was I working with copper and did they make copper closet flanges (and how did they connect them to the pipe)?

I ended up removing it by drilling a couple 3/8 holes, then bashing/"tearing" the metal with a cold chisel. It was definitely not breaking/cracking like cast iron.

For future reference, what material do you think it was, and how do you remove it properly?

As a side note, I used a 3" PVC flange with rubber gasket to inset into the existing pipe. I bought two to see which would work better. One was a PVC w/ metal ring & gasket by Sioux City, and the other was all-PVC w/ rubber gasket by Oatey. I discover two things: 1) the Oatey fit too loosely into the pipe (bad seal), and 2) the Oatey flange is too damned thick (7/16"), vs. maybe like 1/4" thick for the metal ring on the Sioux City. Two thumbs up for the Sioux City from what I could tell.