I thought it was a Stihl at first but it looked too complete and sure enough it wasn't. I was about to leave it when I got a light bulb moment and thought about a spare engine I had that, from memory, was the same as this one. It was. My engine has a missing air cleaner cover which this trimmer has. The head is stuck and won't spin. There looks to be string caught behind what's left of the trimmer head.
Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!