Columbus Tubing Puzzle

[cij28]

I am looking to restore a steel Scapin from the 80's and am puzzled as to what the tubing is. I am assuming it's Columbus as its a Scapin but seller of the frame told me it was slx when I bought it off eBay. I now have received the frame and it measures for a 26.2mm seatpost so def not slx. It's quite weighty so I thought maybe zeta or aelle?

Any guidance on how I can attempt to work this out would be gratefully received.

There is a upside down heart shaped cut out on the lugs if that helps narrow it down at all?

Thanks

Dave