Orso Milano Trumpet - Standard 4.5" Bell - Serial Number: 6372
Thank you for contacting Mearto. This is a trumpet made by Orsi Instruments. They have been producing musical instruments since 1836. The factory is currently based in Tradate, Italy. From what I was able to glean through online reviews and discussions, Orsi instruments are considered mid-range quality, not high-level professional. From your photographs, the instrument appears to be in good condition.
I’ve been able to find only a few of these instruments sold at auction, one closing at $114 and the other $850. I also searched for Orsi trumpets being sold, to see asking prices. Below I have added links to what I discovered.
Based on this information the Fair Market Value is between $400 and $500.