An International one-sheet makes sense for someone with a large worldwide following like Hitchcock, or an Academy Award winner like Roman Holiday from a major studio, but it is quite rare for a 50s movie period, and for a shlocky film like Attack of the 50ft Woman that likely got no overseas distribution outside of the UK would be strange indeed.
I wrote and asked Ed Poole AT LAMP about this issue, with regard to this film and time period. He wrote back:
"You are asking a very in depth and subjective question that depends on the title and requires a lot of research.
Defining 'international'- A poster created in one country for use to publicize their film in another country.
We have records of internationals dating back to around 1906. There is even some possibility of U.S. 'Trust' distributors being the originators of the first vertical quads in England. Before 1910, French distributors like Gaumont and Melies sent Thierry hates "French Grande" posters to their offices in New York for use here in the U.S.
In the time period that you're looking at, internationals were fairly common. Some were marked to tell easily and some weren't. We have numerous on file. For example, take the international poster for the 1957
Jet Pilot. Below the RKO tag it shows it has been distributed by Universal International. NSS handled the printing and shipping and were 'supposed' to take their NSS number and property tag off, but forgot. In a completely different direction, take a look at
Buccaneer from 1958 and you will see an international 3 sheet and lobby card set issued that were different colors than the U.S. material.
During that time period when NSS was so dominant, they started stamping the back of the poster with 'FOR' (for FOREIGN) on the posters that were printed for shipment overseas.
Most titles fall under general guidelines for documentation, but there are massive amounts of exceptions. One of the exceptions is an area that seems to be a little misunderstood, which is 'studio issues'. NSS was paid a royalty for whatever services they provided. When studios wanted to promote a film in advance outside of NSS distribution, posters were printed for them to hand out directly to theater managers or for whatever promotion they had planned. Sometimes these were printed by NSS with the property tag removed (usually leaving the NSS number for identification) and sometimes they were printed by alternate printers. A good example of this would be
Back to the Future. So, you usually have to scrutinize the poster for markings and if they're not specific enough, then more digging is necessary on that specific title."
A public thanks to Ed and LAMP for this information. They are an invaluable source of data and images.