Rare overprints on the first Labuan postal stationary card

The first post card of Labuan was issued in 1881. This was the 4c green on buff card. It bears the head of Queen Victoria similar in design with the concurrent stamp issue. 

In 1891, the card was overprinted 3 CENTS  when Labuan joined the Universal Postal Union on 1 July 1891 and the overseas rate was reduced to 3c. According to Higgins & Gage, both genuine used and unused copies are rare and counterfeits exist. However, the latter's existence has not been proven and almost certainly no forged copies have been seen or classified as such. So what we have here is quite likely to be the real deal. Commercially used copies are definitely going to be expensive.

On 1 November 1907, the administration of Labuan was transferred from North Borneo to Straits Settlements. Evidently, some of the original stock of the 1881 card were around. These were overprinted for use in addition to the contemporary 1c+1c and 3c+3c cards. The overprint used can be seen above. The overseas rate was 3c. All three cards are difficult to find especially when commercially used. The above card should the rarest of these three cards. I dare not speculate how much a properly used copy would cost as it would also be very desirable to Straits collectors.