Hallo Dennis,

You putting me "live" on the Web inspired me to do some serious Web-digging last week-end and I came up with some very interesting manufacturing facts concerning "The Gibson". Facts from the Gibson Company itself.
So I am starting to look like an old man - putting the questions and then trying to answer them myself !
This information will probably straighten the lines when it comes to UB 2 and 3.

The Gibson company introduced a new line of instruments in December 1923 in one version only.
The UB - Ukulele Banjo - a rather simple instrument with a 6" rim that was to be the UB 1 even if it didn´t have any style number at the time.

In the 1925 catalog the company described a series of three UB's in three different styles - the UB 1, UB 2 and UB 3 - all of them with a flat, plate style resonator, the UB 1 with 6" rim and UB 2 and 3 with an 8" rim. UB 3 slightly more elaborate.

In February 1926 UB 3 was fitted with the famous diamond flange resonator made of maple ( thus creating the UB 2 standard and the UB 2 de Luxe - earlier UB3 ).
In 1927 the series were modified, now offering four different models UB1 - UB4 and special made to order, a gold plated  UB4 - the UB 5. The UB 4 and 5 had a rim of walnut and a resonator of burl walnut.
In 1930 (Wall Street crash ?) the UB 5 was dropped from the line and in 1938 the UB was available for the last time but only in the style-1 fashion.

Many of Gibson's banjos and UB's were numbered. Normally with four digits (lot #) followed by two digits (instrument #).
1925 -   8000 - xx
1928 -   8800 - xx
1931 -   9400 - xx
1934 -   9800 - xx

My own UB 5 bears the number 8597 - 53, making it a very early 1927 model.

That's all Dennis !

Best regards
Hans Friberg