Having mainly cleaned 16 size pocket watches in the past, I have recently turned my attention to 18 size. Today I started on two 1890 John C. Dueber grade watches that immediately raise a question. Under the dial, right next to the lever setting and winding mechanisms both watches happen to have the same curious lever that appears hooked to the bottom side of the mainspring barrel. See attached picture. The whole construction somehow reminds me of Abbott stem wind conversions on KW Elgins, that I only know from pictures, but here there’s no Abbott patent text, so I don’t think it has anything to do with that. Not having seen this on other watches, I am curious to find out what this is. Can anyone shed a light on this, what this lever's function is? Thanks!