Bahrain Great Britain Stamps Overprint Missing?

These 3 stamps were hiding in a glassine I finally got to, that was labeled "Bahrain". The first appears to be scott 81. Two of the stamps do not have the "Bahrain" part of the overprint for scott 82:




Is it common for the "Bahrain" to be omitted or is there another explanation? Thanks.

Some info on the omitted types.
http://www.gbos.org.uk/index.php/Country_List/8

Thank you for the link!

For those of you who don't use the link, the stamps without the overprint are from Muscat and Oman, or you might find it under British Postal Agencies in Eastern Arabia.

The stamps without a country name were used at the British postal agencies in Muscat (Oman), Dubai (United Arab Emirates) and Qatar. From 1960, they were also used in Abu Dhabi (United Arab Emirates).

The set comes with two watermarks: Tudor Crown and E2R and Saint Edward's Crown with E2R. The ½ Anna on ½d and 12 Annas on 1s. 3d. only exist with the Tudor Crown watermark. The 1½ Annas on 1½d stamp with the Saint Edward's Crown watermark is very rare. Only one mint copy is known.

In 1957, the stamps with the Saint Edward's Crown watermark was issued with an overprint in new paise (NP). At that time, stamps for use in Qatar were overprinted with the name of the country. Stamps for use in Kuwait and Bahrain have always been overprinted with the name of the country.

The ½ Anna stamp of Bahrain exists with the fraction of the overprinted value missing.

Below is the Tudor Crown set used at the British postal agencies in Eastern Arabia. Due to a shortage of stamps overprinted for Kuwait, they were also used in Kuwait for short periods.

There exists a missing overprint for the Bahrain Wilding stamps. This, however, still shows the country's name.

The overprinting of Wilding stamps for use in Bahrain was done in two operations. First, the country's name and currency were overprinted on the British stamps. Then, the value was overprinted. A number of sheets for the 1/2 Anna on 1/2d missed the overprinting of the fraction.