The Gibson catalogs from the early 1960s do not list an octave mandolin or a Mandola available for purchase but that did not stop Gibson Teacher-Agent Irving Kessler from ordering them. Mr. Kessler owned a teaching studio in New York called the Hawthorne Guitar Studio and was able to order instruments directly from Gibson to sell to students. It seems Mr. Kessler made a habit of ordering custom appointed instruments including an L-5CT Special, TB-250 Special, A-40N Mandola (not yet listed), and this interesting TG-25 factory drilled and set up for use as an octave mandolin with 8 strings.
I purchased the collection of custom ordered instruments along with Mr. Kessler’s clean 1960 Gibson ES-355 from his grandson. The TG-25 OM came to me with an incorrect saddle in place so I sourced a rosewood saddle and bridge adjustment screws as well as a period correct case. It’s now in excellent playing condition and sounds lovely.