I think the Hughes 500 on the right might be VH-BAD. The base of the single letter on the centre panel of the nose bubble is just visible under the JR rotor blade and it looks like it could be a "D". Here is a link to a photo of VH-BAD, another Antarctic Warrior.
VH-BAD(3)
Regarding the "HS" attached to the Hughes 369HS version of the Hughes 500, here is my latest attempt to unravel the various early designations assigned to this type by the manufacturer. This information is based on the contents of various sales booklets and brochures released by Hughes from 1966 onwards and found on ebay.
Hughes 500, Hughes 500M and Hughes 500U
Although certificated as the "H369", the marketing folks at Hughes decided to give the new (in 1966) civilian version of the Hughes OH-6A the name "Hughes 500". The earliest document I have refers to these three versions, the "Hughes 500" which was aimed at the Executive Transport market. The Hughes 500M was similar to the original OH-6A and featured just a few detail changes and was aimed at the export military market. The other version was the "Hughes 500U" which was the basic version for use in the utility role. Only Ship No.1 was flying when this particular booklet was released so the 500U designation was a proposed title for the utility version but was actually never applied to a flying airframe.
Hughes 500E (HE) and Hughes 500S (HS)
The first eleven 500s built from 1966 onwards were a mix of prototypes and early production ships. Five of these were certificated as the "Hughes 369H". Three were retained by Hughes for testing and the other two were sold to customers (Ships No.1, and 6). Four were constructed as military HM versions, two as HS versions and finally the first HE.
The Hughes 500 was, by about 1968, given the designation "Hughes 500E" with the "E" designating it as the executive transport version. This had the plush interior and was marketed as a five seater! This is the Hughes 369HE. The Hughes 500U designation was replaced by the "Hughes 500S" which again was the basic utility version. This is the Hughes 369HS. (I'm not sure what the "S" standards for). The military Hughes 500M was the Hughes 369HM and was also sold to a few civilian customers, EI-AVN and EI-ATY being two civvie M's. It seems the the Hughes 500E and 500S designations weren't really pursued by the Hughes marketing department and the "real" Hughes 500E didn't appear until 1982. The design was further refined in 1970 and was marketed as the Hughes 500C from there on, while still retaining the Hughes 369 HE and HS certifications. The C was the final production version of the 500 with the four-blade main rotor and Y-Tail.
What actually constitutes a Hughes 500C is open to debate. Is it a 500 with a C-20 engine and metal tail rotor blades or does a 500 with the C-18 engine and metal tail rotor blades also qualify as a 500C? Many will tell you that there are plenty of 500s marked up as "C's" and have the C-18 engine so I'm not sure. The marketing literature does refer to the C-20 engine as being part of the upgrade. I hope this helps but it may well muddy the waters further!
500 Fan.