They make different lenses for different size cctv sensors , you want the 1" sensor models not the ones made for smaller 2/3 " and 1/3 " sensors as they vignette too much. - They are not knock off lenses they are different models that is why they have different model numbers.
there is an older pentax cosmicar 25mm f1.9 with zebra markings
and the newer pentax cosmicar 25mm f1.4 - smaller a better lens
there are 3 versions of this - original made in Japan , then a made in china version and the latest is made in Vietnam
optically they are all the same - I have all 3 there is no differeance
all Fujinon lenses I own are made in Japan - I dont have any not made in Japan
do not confuse Fujian brand with Fujinon
Fujian is a Chinese CCTV lens maker - their lenses are no way as good as Fujinon of Japan.