How are the Director dropouts held together

I did a post a few days ago listing the Director patent. It was chalk full of interesting stuff. But the question quickly came up: How is the dropout insert held in place. The drawings show a seam weld, but those don't appear on production models. Eggit helped clear it up with some rawing and bluing of his:

Dropout insert from patent


Eggit's photos show spot welds holding it together


Edit: Comment from G

No spot welds.

Read the patent, look at fig 5 and item 67 in particular...

G.