I can't say I exactly recognise this upside-down exercise, but I have seen something similar in the rigging climbing display of the Royal Navy, perhaps Royale Studio's Basil Clavering had a Navy connection.
More shapely bodies and splendid shorts here - oh for a better copy!
Erotically speaking, the prime point of interest is the right hand student, apparently slacking in the previous picture and now receiving special 'hands on' attention from the instructor. Note bottom and face in close proximity. Coincidence?
'These are my boys' the instructor seems to be saying, in fact it's almost as though he's hanging them up like a fisherman showing off a particularly fine catch - which they clearly are! It's a really nice image. The instructor oozes power and confidence while the boys display their complete obedience to him, even to the extent of performing together in this girly, 'artistic' display.
Truly a mitchmen putting of men in their place.
Interestingly, there's also a reverse way of looking at this group. The boys show off their fine figures and abilities, they tower above the instructor making him seem diminutive and relatively unfit. He is reduced to propping them up as the stars of the show. I guess it's a matter of personality which way you choose to see this image. An interesting contradiction. A timeless truth about the nature of power.
Meanwhile, the third student dangles from the wall-bars, forgotten at the back. He was presumably intended to provide the apex of a triangular composition, but headless and not quite central enough it just fails to work. Possibly it has been cropped to give more prominence to the foreground group. He has the consolation of the instructor's head nestling in his crotch. Coincidence? I don't think so.
A footnote on clothing:- I think I have mentioned before that Royale provided specially-tailored clothing for their models, to accentuate interesting regions of the body. The unsymmetrical positions of the belt loops on the instructor's trousers suggest they've been 'taken in' to display his backside better. But in this set it's the crotch hugging shorts that stand out and you can see that all three students are sporting frontal 'cleavage' as well as rear. There are no revealing belt loops at the front, but in picture 8 above the centre model has an 'offset' rear loop as though it's been altered too. Fred's thigh hemlines, 11 above on the far right, look great but the two centre models garments look quite odd. It could be that they are just tucked in to show more thigh, but in picture 8 you can see that they are very tight and so short at the back, that the lower buttock cheek is on display. I'm wondering if the baggy frontal effect is partly a result of imperfect 'down-sizing'.
There's probably another factor in play here too. Royale had a trademark technique of wetting clothing to make it cling. It's not so obvious in this set as some, but have a look at the shorts creasing in picture 9. Check out also the singlets in picture 11 above. The seams are much whiter than the body of the vest and you can just see a nipple showing on the middle man, both of which could be a result of wetting which would explain the saggy shorts look - and possibly the glum demeanour of the boys too!