well to the alarm side got a 50's alarm a couple of 70's alarm and one 80's I keep the 80's mech one and a gold plated 50's / 60's one will add pic's of them ... they all had two barrels as you say one to charge the watch one to use as an alarm . and not sure how they could do it off one barrel but in the pic does look like their is a button on both sides of the crown to work two leavers possible . just trying to find the listing again think their was two key holes but took that for winding and setting .
some times the alarm hand is different to the others so it is easy discernible but with very early pocket watches am a bit of a lost if pin and barrel think what 1900's ? so just not sure