To speak to the original question, obviously this is a Lloyd Loar signed F-5 (as was Monroe's instrument). There were about 230 of them made from 1921 to 1923. Loar was an acoustical engineer who closely supervised the production of the F-5's during his tenure at Gibson, and those 230 F-5's are the Holy Grail of bluegrass mandolins. I started a thread on them once. It is at
"http://www.mudcat.org/thread.cfm?threadid=33904#349879">Lloyd Loar F5 Mandolins
but the posts are out of order--it started with my post May 3 /01 at 12:28 p.m.

Many serious working musicians own Lloyd Loars and they are of course equally sought by collectors. They do not come up for sale often, so there you go. No doubt Gibson has made tens of thousands of F-5's over the past 80 years, but the ones associated with Loar are the only ones that go for six figures. An extremely fine F-5 that is NOT from the Loar era, but may have other historical interest, might fetch $20,000 US.

W-O