Orville Gibson signed 1900 f mandolin. Orville Gibson's personally-built (ie non-factory) instruments bear a label with a date and his signature. This particular instrument is quite unusual. The body shows all the signs of the final flourishes on Orville's design just before the factory production started. The hollow-neck design is evident here, as is the non-recurved top (you can clearly see the arching around the edges of the instrument).
Interesting to note- the tailpiece is a factory "the Gibson" Style from approx 1904-1905 (the earliest factory tailpieces had a hole in the top center). The peghead with Star & Crescent Inlay appears to be circa the factory as well, as earlier Orville pieces have banjo-style tuners that were friction pegs. Finally, the fingerboard looks to be the A-model style, rather than the florentine with the extension that partially occludes the soundhole.
From Fred Oster, Vintage Instruments