There is not much to say about OSSA's wheels. They are pretty standard 18 x 2.15 and 21 x 1.60 trials wheels - which is great because replacements are readily available.
The early rims were manufactured by Fa-Ba in Italy, but I do not see anything like them in their current catalog. My 2015 bike has Morad (but unmarked) style rims. I really like the Fa-Ba methodology for tubeless tires in which each spoke nipple has an O-ring seal.
Fa-Ba O-ring sealed nipple assembly
Valve stem and its O-ring
Wheel bearings are a maintenance item. Replacements are commonly available. To the best of my recollection, they all have a rubber seal on both sides.
Rear wheel, disk side bearing 6004 (20 x 42 x 12mm)
Rear Tubeless Tire Mounting
Here is a tip. Prior to mounting the rear, inflate an 18" tube inside the tire to stretch and expand its sidewall. This is best done at least a day beforehand, preferably out in the sun.