ᐅ Adjusting the contact pressure on old Weidtmann door fittings

Hello everyone,

I have some older windows with Weidtmann door fittings where I would like to increase the closing pressure.
The pins can be adjusted using an Allen key. At first, I thought the pins were eccentric, allowing for adjustment, but they don’t appear to be eccentric, and turning them doesn’t really make a difference.

Does anyone have an idea if and how the closing pressure can be increased on these windows?

Attached are a few pictures.

Regards,
Simon