A good chance of being an original seal, with the lip for the glass to close on to:

Simple butt joint in the upper rear corner, not welded, has never caused a problem. May have shrunk back a bit over the years!

A possible cause of doors being difficult to close with new seals: This is my V8 where the doors are easy to close but it is the same as a pal's 78 which were hard to close without the door cards fitted and impossible with them fitted. The seal flange bulges towards the door beside the dashboard in comparison with the vertical section beside the hinge (left). With the door closed (right) that bulge is only a few mm away from the waist-rail bracket instead of getting-on for 10mm as it is everywhere else:

On my pal's 78 I had to dress that bulge back to give more clearance and it made a big difference.