Loose opening lever

[mrbeil]

I recently came into an old side by side shotgun of unknown english make, and the opening lever to crack it open it very loose in the sense that you really have to force it to right in order for anything happen. Is there a fix to this?

 

[mrbeil]

After closer examination, it appears the culprit is a broken spring. What would my options be seeing as how this shotgun is at least 100 years old?

EDIT: Here's some pictures of the spring in question, and the markings on the barrel/receiver to help try to identify the maker