According to the article this was a "clone" of the Mossberg 500 so it may or may not have been a faithful reproduction. 
Well, the Mossberg 500 hit the market in 1960 as a single action bar design. In 1970, after Remington's patent on "dual action bars" ran out, Mossberg altered the design to incorporate two slide bars. Other than that, variations chambered for the 3.5" 12 gauge, the 590 series with easy clean out magazine tubes, and the Maverick 88 crossbolt safety version and so on.
So over time there have been some parts that don't interchange between variations. However, to the best of my knowledge, the basic design of a saftey stop on the internal hammer, (think of the saftey stop on the Series 80 Colt govt. mdl. hammer), has been a standard fixture in all Mossberg 500 variations.
This can be demonstrated on any of the 500 series, by opening the action a
very small amount from the full hammer down position. The slight opening will just move the internal hammer back to the stop notch/safety sear position. If the action is then completely closed again, the hammer will fall a very short distance from the safety stop position when the trigger is pulled.
I am not aware of any copies of the Mossberg 500 series being made by any other manufacturer.