Hi everybody !!
I recently acquired a Dent of London pocket watch that has an unusual jewel setting only on the escape wheel (besides the jeweled balance). I was just wondering what the reasoning was behind only jeweling the escape wheel ?
Thanks guys.
Francesco.

Just a guess, increased time accuracy? If its old enough its possible its part of a move away from 7j watches.

I think the view was based on rotational speed, in other words where is the most movement or rotation and those would be expected to be jeweled first since the most wear/friction would occur. 1st would be the balance mechanism with 7 jewels so the most logical step if you were to add 2 more jewels would be the escape wheel, but some would add the jewels not in pairs but what could be seen on the visible plate but these are oddball rather than the rule.

Thank you Jim and Claude for your interesting answers!

Adding a pair of Jewels to the Escape arbor would be the best way to up-jewel from 7 to 9 jewels for better performance. The Escape wheel turns 14,400 times each hour which is 1/576,000th of a "full wind".

In other words there is hardly ANY power trying to turn the escape wheel and so jeweling it for "0" friction is a good improvement. Certainly better than some watchmakers who jeweled the pallet fork next instead of the Second (4Th) wheel.