Complex sentence: Murphy stopped his association with Gerber and made approximately 90,000 Murphy Combat knives marked on the handle as such for servicemen during and after WWII and these knives are now considered highly collectible by military knife collectors and are fairly scarce despite the large number made.
Split into simpler sentences: Murphy stopped his association with Gerber and made approximately 90,000 Murphy Combat knives. These knives are now considered highly collectible by military knife collectors and are fairly scarce despite the relatively large number made.