I had my nikkormat ft3 serviced. when i collected it, there was a gum like substance in the light seal. the light seal appeared to be scraped out and not replaced. the shop claimed the gum substance was a modern light seal which will never need replacing. any ideas? also the meter is very jumpy on iso 400. today even at 1/1000sec the needle jumps without a lens on. I would have thought that 1/1000 was fast enough @ iso 400 to not read overexposure. what is this light seal?