Hi Rodney,

Thank you for contacting Mearto with your appraisal inquiry.
You don't specify the identity of the professional musician who played this; in some cases, that provenance might make this trombone more valuable than the $400-600 it's currently worth at auction (and based on recent auctions of similar instruments).
Based on the photos and information provided, and subject to examination, this is:

A vintage Holton Special silvered brass tenor trombone
made by Frank Horton & Co, Chicago, circa 1930s-40s
The bell engraved "Holton Special / made by / Frank Holton Co / Chicago", together with a lined hard-sided case (probably not original.
DIMENSIONS - standard
CONDITION: This trombone appears to be in good condition without visible dents or repairs; value assumes it retains some musicality and does not have any missing parts or repairs.
PROVENANCE: Inherited; played by a professional musician while in college in the 1940s
$ 400-600*
*represents a fair-market value for auction purposes; retail or asking price may vary.

Please let us know if you have additional items to appraise, or questions/concerns, and thank you again for using Mearto.
~ Delia