FREE Very old and valuable US Stamp from 1879!

Here's another VERY old US stamp-- it's a 5c blue with a portrait of 12th US president Zachary Taylor, I *think* it is Scott number 185 from 1879, although I am NOT an expert on US stamps. If I'm right, it has a catalogue value of $17.50, so not "some cheap piece of junk!"

It is in used condition with part of a town cancel at left and the number "22" at right. There are no perforations at left, but that was natural with the edge of sheets of old stamps. There are some bits of old paper and glassine stamp mounts on the back (see 2nd picture), but otherwise looks OK.

Here's the bigger scoop: Both my parents passed away in the last 3 years, and they were borderline "hoarders." My stepdad collected stamps, and this is from his collection.