For the most basic info- appears to be a rimfire cartridge. Next time, stick a ruler in there so we can get an idea of size. While the .22 rimfire is a very common round, in years past rimfires were made in many larger calibers- 25s, 32s, 9mm, 38, 44s, etc.
If you said headstamp was "U", my repsonse would be Union Metallic Cartridge Company- but the shield (Crest is a toothpaste) was the logo for Rheinisch Westfälische Sprengstoffwerke- or as most of us call them- RWS of Germany. I did find mention of them for whatever reason using a "U" headstamp at one time. It is now a letter "R" in that same shield.
BTW- they are still in business- subsidiary of RUAG. You might hunt them up, and drop them a question.
What we have here is... failure- to communicate.