The most common forgeries of North Borneo were those from Francois Fournier at Geneva(1846-1917) and Rene Carame in Paris of the 1889 postage & revenue issue. They have been shown previously and would not be mentioned here any further.
The item on the right is a Fournier forgery of the 1894 $1 adhesive with the letters FAUX or false in black. This was obviously well produced and comparisons can be made with the genuine stamp on the left.
Firstly, the lion is different with a straight tail with a blunt ending. There are less dots around the lion. The motto Pergo et Perago is smaller with letters c instead of g. There are a few other minor differences as well. This item was probably lifted from one of the reference sheets of Fournier forgeries. I am not sure whether there are perforated examples of this forgery without the FAUX overprint.
These forgeries of the 1886 issue are ascribed to the Italian forger Nino Imperato(Genoa) or more likely Erasmus Oneglia(Turin). It was thought Imperato acquired his stock of forgeries when Oneglia retired in 1920.
The cancellations and gauge of perforation would correspond to documented examples of some Oneglia forgeries. Most of his forgeries were produced singly from a lone die and would have to be perforated and cancelled individually. Note how the Chinese characters for 2c remain the same for all the values of this forged set. These forgeries are more difficult to find than the genuine stamps.
Two Kamigata forgeries with different colours to the original stamps of the 1894 set. I can confidently ascribed these type of forgeries to Maeda Kihei of the Kamigata-Ya shop in Tokyo, a Japanese dealer in the 1890s and 1900s who forged stamps from about 27 countries, mostly Asian for sale. These are collectively known as Kamigata forgeries. They are generally crude and lithographed. Some are cancelled with partial circular cancels bearing the letters IMITATION.Reference; The Fakes, Forgeries & Experts journal vols 5 Varro E Tyler.