Landy wheel cylinder question

HI Guy's new here so hope I'm in the rite area
I'm from the Agricultural part of Australia and my late uncle was a dryland farmer, he was a Land rover only bloke , he had a few, and range of years, to cut a long story short after he died I purchased his 4.5 tone trailer, he used it to cart scrap steel behind his long wheelbase land rover.
he ran Landy hubs on it to utilize his spare rims and tires.
My question is , It has a buggered wheel cylinder on the front right (its got drums all round tandem axle)
and I have no idea of what series hubs or drums it has on it and wondering if anyone can tell me what cylinder I need to buy , any help appreciated.
I gather its early, the trailer was used by our electricity trust(government called ETSA) its a great strong trailer I think it would have to be 60-70's , last pic ,I think the fork is about 5 tone bit over loaded,


https://www.dropbox.com/sc/ehyg8hxul1vk4kq/AAAlpqWpZ8FsZo9R8gw3EKk1a
https://www.dropbox.com/sc/q6w0dul6q6gcp9l/AAABslv4jtAE2g0nw3yWlQpaa
https://www.dropbox.com/sc/tdjdptenf9i6t33/AAAMhRQuslraGSl5QaebVggsa

They look pretty similar to early 90 rear wheel cylinders which I think we're similar to late series cylinders. Can you post a picture of the back of the wheel?

Ask a guy called James Martin on here - he will likely be able to identify it