A Brunei JO cover

I am showing this JO item which is probably authentic but one can never be entirely sure. It was philatelic in origin. It was postmarked at Brunei Town which is a bit more unusual as most of these covers tend to have a Kuching postmark. The lack of a censor chop was because this cover did not contain any letter inside. It was sent kosong in local speak. Another likely explanation is that these type of covers never went through the post. They were cancelled by favour and then collected by the owners.

The most valuable stamp on this cover is the is the 2c green and not the 50c or $1 stamps. If one adds up the individual used stamp values here it amounts to a respectable sum which in practice, one would not get at an auction. It is probably more valuable if each stamp is cut out and sold individually on piece but that would have amounted to philatelic vandalism!
The Japanese date here of 17 1 2605 would correspond to 17 1 1945.

Just to point out the variation in the first character Dai or big reading from left to right. I previously thought it was part of a fake cancel. One reliable way to know whether this one line overprint is real or not is by looking at the fifth box looking character Koku. It should have one or two faint small dots at the upper part of the empty space on the right side as seen here. But it is not invariably present. Most of the stamps on this cover do have it.

The other variation is in the colour of the overprint. The one here on the 12c stamp is blue rather than violet. The others are red and black even though I have never seen this overprint in black on a Brunei stamp. You can see the rare red overprint that is in my collection by clicking here.

A few values were printed in red but not found to be satisfactory. This was believed to have been carried out early on in Miri. The ones overprinted later were largely in violet but it can be seen on this cover varies from from light to deep shades.