Ex Mod Ignition Distributor

Hello All
Im new to my
1984 (I Think)
Series 3 109 Ex Mod
2.5 petrol.
I am curious as to what the sealed distributor uses for vacuum advance , if it uses it at all.
theres no vac line no vac diaphragm

Is it centrifugal ??
It has a new old stock distributor installed before i received the truck.

Thank You
Jim

Sounds like a question for Les.

Bumping
I have two old units ill have a look myself
If les chimes in
may be he has the "knowledge"