I just picked up a 6309-7049 the other day with unknown service history and I am currently sourcing replacement gaskets for the caseback, crystal, and crown. I realize that the silicone helps the gaskets waterproofing properties, but just how important is it?
I also own a modern skx diver and I have never noticed any grease on the caseback gasket before, however I have taken it in water several times with no issues.
I doubt I would ever have the watch pressure tested or down to any great depths, but I would like some peace of mind should I decide to take it in the ocean with me.
Thanks for your input!