Although I have seen similar Cyma Watersport timepieces with small hands which were all the same, it looks quite original. The use of different replica omega Seamaster Pro 300m Seamaster 300 watches small hands was and still is not that unusual, think Breguet TransAtlantique for example. The unsigned winding and time-setting crown seems to be perfectly original as well.The sub dials have these amazingly nice circular grains, as found on the Omega Speedmaster (pre-)Professional models as well.
The movement in this Cyma is a Valjoux 72, replica omega Seamaster Aqua Terra watches as used in the famous vintage Rolex (Oyster) Daytona models from the 1960s and 1970s. This hand wound movement has been used for many other watches as well and is known to be a solid timekeeper and chronograph. The late Chuck Maddox found a vintage manual for this movement and published it on his website in 2004, you can find it here. This movement has a beat rate replica omega Speedmaster Professional watches of 18000 bph and a power reserve of 46 hours.The case back is a snap-on type and has no particular engravings other than what seems to be a reference number of some sort. In the back side of the lugs, you can see a screw in each of them, which probably holds the bezel or movement in place (hard to tell from the exterior).