It is the old "New Hammer"... I do not know from which year, but I have seen one in shop at least in 2004. Im not fully informed about the history, but imho there was the original Hammer pump from Kingmann, what should be the rival of BE Tigershark and such like cheap pumps. The original has used similar frames like the old Spyders and the barrel was Spyder-threated. Then came the "Hammer A" and "Hammer P" versions (on which are imho different only the gripframes - from aluminium or plastic - with different price tag). After these there was "New Hammer" - the last and cheapest variant (Kingman Hammer | Paintball Review | pbreview.com
There was likewise Hammer 2 what was Sterling style pump and was anounced even Hammer III what should be in-line semi. But that is different story.
The old "New Hammer" in the stock condition is not just great marker - nearly the all stock screws are bad, the stock trigger-safety do not works reliably long time, there are no ball detents, the plastic frame is weak, likewise the conection of the sight rail with the frame and he has "powerfeed" which is in the way of the "iron" sights. The original brass hammer is here to heavy and the powertube has small diameter. With common 9oz tank in backbottle setup there is bad gas/liquid CO2 separation, with powerlets you having really bad efficiency.
But when you change the stock screws, strengten the frame, add detents, use raised sights and tank with siphon tube, then you have really, really great CA marker. You need be only a little gentle on him because the resistance to damage is even after such like changes not great, but otherwise, the lifetime should be big.
The basic construction of the important parts is here simple, but not bad, the parts are rally good manufactured and made from good materials. The Stock barrel is simple and rought from outer diameter, but it is very good medium bore (17,5mm / 0,689") barrel. I have hat +/- 0,1 fps consictency with such like marker going on liquid CO2 with best paint.
My New Hammer has now modified nearly all original parts (exception are perhaps the pins in the trigger :-) ) and in many aspects he performs like best high-end pump-markers. For example the clearances of the pump handle have been minimized nearly on zero with new PTFE pump handle insert and with modification of conection of the bolt with the pump rods, the all surfaces here are polished and having very small friction.
This week I have performed another two interesting tests (modified PT + valve nut and new valve spring), today I will make another (even lighter hammer). Im hoping for significantly better results than the best last what are here published.
I will put the results here in Monday.
And then I will perhaps modify the stock bolt, which has imho excessive spaces for CO2 expansion in front what wasting imho some gas and reducing thier efficiency.