In the early 1920's there were only very few pen makers in Italy. The market was dominated by import products which came from the US, England and from Germany. General agents for major brands such as Waterman or Parker, organized advertising campaigns to make their products better known to the public at large.

The general perception was that fountain pens were imported products and thus trustworthy.  This is the reason why on many early Italian pens we find English definitions such as "Safety"," Fountain Pen" engraved on the barrel; this would help domestic products to be more appreciated by the public who would think they were not Italian. At the time, being foreign meant being fashionable and desirable. 

When Giuseppe Tibaldi started his production of pens in the second decade of the XX century ( the brand Tibaldi was registered in 1916), he was a sort of a pioneer of the pen industry. Thus, before he decided to use his own family name as a brand, he tested the market with a line of foreign-looking  pens called The G.B.T. Pen - London.

The initials stood for Giuseppe/Giovanni - Benelli -Tibaldi since both Tibaldi and Benelli' first names (Giovanni Benelli was Tibaldi's business partner in charge for the technical development of products) began with G.

London was just the nice-sounding name of a foreign city which would help the pens to sell better.

These early G.B.T. Pen products are slightly different from the Tibaldi safety pens which would start being marketed later on. Tibaldi safety pens have a very German style, with long cap and rounded turning knob, while The G.B.T. pens more or less replicate Waterman's design of the turning knob with flat ends and the addition of a light decorative engraving.

https://www.tenpen.it/product/tibaldi-safety-pen-nr-3-long

This design would be then replicated with slight adjustments for the Mascotte line of student pens which Tibaldi marketed a few years later.

https://www.tenpen.it/product/tibaldi-mascotte-safety-pen

Nibs on The G.B.T. pens are "warranted" but the design is exactly the same as Tibaldi nibs.

This pen is a little gem as it came in unused condition with its original sticker still attached to the barrel. The nib is very pleasant and extremely flexible, like all Tibaldi nibs found on safety pens.