John, your "Original F Mauser" commentary is meaningless when the OP's rifle is clearly not an "Original".

The Zastava produced Intermediate Commercial actions often used by Heym. Also used in Monkey Wards produced rifles as were their Std Length actions. The Intermediate Commercials lacked the charge hump and thumbcut. They did use military bottom metal converted to hinged.

[Linked Image from i.imgur.com]
[Linked Image from i.imgur.com]
[Linked Image from i.imgur.com]

Here's your "transitional" FN Commercial:

[Linked Image from i.imgur.com]
[Linked Image from i.imgur.com]