They are motorcycle shocks made by Amstrong in India. I helped fit a set only a few weeks ago at our airfield.
That's the trouble when you wander around aimlessly on a Saturday morning at the airfield, you get put to work!
I remember having a good look at the box that they came in when I was putting it in the bin for the owner, it had the name Armstrong and made in India written on the box. They are way, way more stiffer than any mountain bike shock absorber.
I pushed my 100 kg body on top of them and they wouldn't even budge, I guess the aircraft is around 300 kg and when they are mounted they didn't compress at all with the weight of the aircraft, they only compressed with the pilot seated in the aircraft and then only a few millimetres I'm guessing. They must be for a pretty heavy motorbike because they are heavy, I'm guessing a couple of kilograms each.
They were replacing a set of fournales (I think that is the spelling) they were a nitrogen filled shock absorber but instead of having a spring on the outsidethey just worked with oil and gas. The chrome on the main shaft which I am guessing is about 30 mil diameter had started to peel off after about 15 years and it allowed the gas to escape because it damaged the seals. They looked like a very short motorcycle fork if that helps but the owner replaced them with conventional shocks because he said the other ones were no longer made. The gas shock absorbers would be lucky to weigh 500 g each so they were very light in comparison to what was put back on. To replace the shock absorbers on both sides only took around 25 minutes total time, the engine didn't even cooldown and the owner headed back to Boonah.