I have been inside my own F3P and seen in person as well as reviewing the Nikon official repair manual and parts list for both the F3 and F3P/T and the weather sealing for the P/T is mostly done with silicone rather than Neoprene and the weather sealing of my F3P has not deteriorated *at all*. I cannot vouch for the Canon products, but if they used neoprene then in all likelihood they have deteriorated and will not be sealed. I got my F3P in 1993 and it was my daily news camera for ten years as well being used as a regular camera for weddings, I consider mine to be as weatherproof as I'll ever need, but, Your Mileage May Vary.