Vintage Military Band Brass Lyre Shaped Music Sheet Holder

As used by the marching military bands in the brass section, it would strap over the instrument to hold the sheet music, I'm not sure for what instrument but the brass lyre shaped holder is set off centre to accommodate the relevant instrument, there are no maker marks and it comes in used condition, the leather strap which has been white dubbed is well used and the brass needs a clean , hard to measure but roughly 5 inches long.