Citroen merged with Peugeot in 1976, so it is entirely possible that the Citroen-branded engine in your Peugeot is a “normal” state of affairs. Because neither marque has been sold in The US–where 99% of our forum members reside–for several decades, it’s not likely that anyone here can provide specific technical advice regarding either of those marques.
Swapping in a different engine in a modern, computer controlled car like your 2007 is VERY difficult, I can’t think of why someone would go to all that trouble for a 207. So I agree, I bet it came that way.
Edit - if it is an engine with a Citroen label, it probably was a replacement for an identical Peugeot-labeled engine that was swapped out because of some major engine problem.
Google ‘2007 Peugeot 207 engine’ and look at the photos, I bet one of them matches your car.
The 207 was based on the Citroen C3, and it’s a reasonable expectation for the two cars to share a lot of gear, including the drive train. It’s the original engine.
Likely entirely normal. Back in the late 70s when Chrysler came out with the Omnis those cars had VW Rabbit engines in them. Even the valve covers were stamped VW.
And my parents had a late 70s Chevy with an Oldsmobile engine in it.
+1
For a brief period of time, Chrysler was installing Peugeot engines in those cars when there was a shortfall in the supply of VW engines. Imagine the confusion regarding replacement parts for the few customers who got Peugeot engines…