Where are slotted cap jewels used?

[Kalanag]

I wonder what slotted cap jewels are for and where they are used.

This is an KIF 501 with a slot:

 

[mikepilk]

I have a Vertex Revue Nautique with a MSR T43 movement which has the cut outs in the cap jewels.

I too was puzzled, so posted about it, but cannot find the thread.

I think someone suggested it's so they can be oiled without dismantling.

[jdm]

14 hours ago, mikepilk said:

I think someone suggested it's so they can be oiled without dismantling.

That's what I'm thinking too. Then someone in an higher echelon identified who theorized that being able to freely add oil without cleaning is a good idea, the additional cost for the special jewels, sent him back to assembly work and the novelty quickly disappeared.

[clockboy]

I would have thought the only logical reason is so they can be lubricated without removal. However surely as they are open and no protection from dust etc so they still need cleaning so IMO just a bad design. 

[nickelsilver]

Well OP's post the slot goes over center, so no idea at all, total nmLystrt