Based on my minimal research, this 13-star flag appears to be in the medallion design used for the 1876 Centennial. We have had possession of this flag for an estimated 40-50 years and it has always been behind glass and in a securely fixed frame in our attic. Flag size is approximately 2.5' by 4'. The cloth seems to be wool.
We believe this flag was found with other items in grandparents attic that we inherited. No other pervious details are known.
Thank you for submitting your item for appraisal. This appears to be a centenial flag from 1876 in good condition with 13 machine-sewn, ( most likely double-sided ) cotton stars configured around a larger central star on, flanked by stars in each corner. The fly and part of hoist is constructed of 13 machine-sewn, cotton fabric stripes. Two modern grommets in the hoist. Judging from the fabric combined with the provenance you provided it appears to be an older flag.
The estimate is base on similar flags of good size sold or offered at auction.
"Asking prices" in the trade can be higher and vary.