I'd say "IV" refers to the length of the action. Sako uses different lengths of action for different calibers. Today they run from XS upwards, but the previous model was labeled by numbers.

On the Sakos I've seen - and they're plenty - the model name is also enscribed on the barrel.

As to the "imported by Stoeger" I have no comment.
Some photos would help for sure.

You'll find detailed info on the 75 here.
It mentions a detachable magazine, so I wonder if the magazine box is a U.S. market feature? On older models there used to be also magazine boxes.

- Lars/Finland