#42 City revenue stamp from Japan.
Ray Chen

#45 Found in Michel as Jugoslavia/Croatia #21, 1945, surcharge applied in Split.
Rick Scott

This stamp is classified by Michel Germany as Feldpostmarke #3. Issued in November 1944 to allow families to send goods to their soldiers on battle fields. Its value is pretty high if originally cancelled, even higher if it's on a fragment or an envelope. Beware of forged cancels.
Stefano

These are indeed stamps issued by the Bavarian State Railways. They also exist with the inscription "Kgl. Bayer. Staatseisenb.", an abbreviation of the German "Koenigliche Bayerische Staatseisenbahngesellschaft", which translates as "Royal Bavarian State Railway Company".
These Bavarian State Railway stamps were issued in a variety of colors, all in the same basic design -- including a spoked wheel with angel- or eagle-like wings on both sides. These stamps were issued for the prepayment of the charge for shipping small parcels by rail.
Many countries (as well as private railway companies, in the U.S. and elsewhere) have issued these, including Great Britain, New Zealand, Prussia, Imperial Germany, etc. However, the major postage stamp catalogs list only stamps issued by governments, not those issued by railway companies -- even those that, like the Royal Bavarian State Railway Company, are actually government-owned.
Neal Bruckman

This is a railway parcel stamp from the Bavarian State Railway. The Dusterbehn catalog lists 52 different stamps issued between 1904-1920.
Rick Scott

Stepanakert is the capital of Nagorno-Karabach, an autonomous region in Azerbaijan that wants to be (is?) independent. I've seen a variety of stamps from this area, but no catalog. Like the other ex-USSR "locals", most are likely to be private or bogus issues.
Rick Scott

Agree with Rick, most likely to be bogus, but some Nagorno-Karabakh have been found on international mail. My attempts to respond to mail, addressing the envelope either
Stepanakert, via Armenia
or Stepanakert via Azerbaijan
have been returned with an endorsement that they cannot be delivered by reason of war (written in French, international post language).

You're exactly right. Most modern British definitives exist with overprints to identify their users, to make them (exactly like perfins) difficult to use by anyone else.
However, you'll never (I think) find one postally used. These stamp issues are valid for either postage or revenue use, and you'll only find them overprinted to pay documentary revenue tax.
Neal Bruckman

This appears to be a security overprint from Great Britain. These stamps were overprinted with initials or companies' names for the same revenue protection motivations as perfins, but those I've seen have been used for revenue rather than postal use.
Rick Scott

The NTGB overprint is indeed for non-postal purposes. I believe it may stand for the "National Trust of Great Britain", but that's only a guess. These are more common on tax bills from gas and electricity companies.
Thomas M. Fortunato

This is a security overprint (performing the same function as a perfin). It is also correct that these were usually printed on stamps used for revenue purposes rather than for postage. However, the obligation to pay a 2d stamp duty charge on receipts was abolished many years ago (at least in the early 1960s).
The correct name of the National Trust (a leading conservation body) is 'The National Trust for Places of Historic Interest or Natural Beauty', and I'm afraid that the 'NTGB' on this item is more likely to be 'North Thames Gas Board'!
Andrew Riddell