Welcome to the Forum. We'll try and help you as best we can. You can post pics from another site, like photobucket, Flickr, etc. The serial dates it somewhere between 55-56. Go to
Horn-u-copia and scroll down to the Blessing thread . They have pictures of some trumpets. The Standard was the grade above the Scholastic and below the Artist and Super Artist which were fine horns. Here is a link to Blessing history
History I would say yours is in one of the better eras of Blessing horns. I would check the slides for whether they are free or stuck and how the 3 pistons go down and spring up. Did it have a mouthpiece with it? You might check Ebay advanced search for completed listings and see what has been sold. The value is hard to say, It may need a good cleaning and lube of the slides and pistons if it has been sitting a long time. Check it over and get back to us.
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Dave Rafferty
07 Barrington Trumpet,
1972 Reynolds Medalist
55 Besson 8-10 trumpet
55 Roth by Reynolds Cornet
73 Olds Ambassador Cornet
30's Czech small bore Trumpet
Getzen 80 cornet,
33 American Standard cornet
www.kalamazooconcertband.org