it looks like Rhenus was a post war trademark of Eduard Kettner in Köln and Ketnner was selling different foreign made guns under this label.
Ketnner dont exist anymore in germany but is still in business in austria https://www.kettner.com/at_de/waffen/gebrauchtwaffen.html. I found M 98 hunting rifles made in former jugoslavia sold under the Rhenus brand and this 22 WMR rifle close to yours https://waffenforum.gun-forum.de/thread/42818-lakefield-rhenus-22wmr/

its a stamped with Rhenus .22WMR - Made by L.F.A in Canada
so this may explain the maple leaf sticker

"Since Lakefield Arms was established in 1969, it's been manufacturing light firearms for customers across the world.

Now called Savage Arms Canada, the firearm manufacturer opened its doors to tours on Saturday (June 17) to show people the process of how guns are made. Ticket sale proceeds were donated to the United Way.

The company Savage Arms was established in Utica, N.Y. in 1894. In 1995, Lakefield Arms was picked up by them, and they became Savage Arms Canada."
https://www.mykawartha.com/news-story/73...-guns-are-made/

so it looks like your gun was made by Lakefield Arms in canada, today Savage Arms Canada
the little gun was probabyl made on special order for Eduard Kettner in Köln/ germany , than found the way to spain.