I have a Gibson open back banjo that I believe is an RB-180 although I find no verification of that. I do however have a number on the headstock of 700621. I find the Gibson numbering to be quite confusing. What and when was this banjo made. Thanks.
If it is an RB180 then it will look like this. The RB180 had a Mastertone ring which was not very popular with the long neck crowd. The lighter weight RB175 was a lot more popular. The RB180 was only made from 1961 to 1968. I could not find the exact serial number but, from the closest number I could find I would guess 1967 or 1968. Don't take that for gospel, it's an educated guess.
RB170 was the regulation length open backed banjo with 22 frets. It used to be something of a sleeper but seems to have attracted a following in recent years. It is well suited to old time playing. RB175 was the long necked version of the RB170 which was much more popular than the RB180 I pictured above and was frequently used during the folk boom. The RB180 was a bit of a disappointment to the folk crowd with its weight and mass.
John, the RB180 did have neck binding. Ira, the Mastertone style ring made the banjo much heavier than the RB175 and the RB170 which both used the small brass hoop. From what I have gleaned, the heavy tone ring not only added a lot of mass to the banjo but also produced a lot of sustain that was not favored by the folk banjoists of the time.