Transrotor TR9.1 : based on what Rega type ?

I am confused about the Transrotor TR9.1 tonearm. Some people say it is based on the Rega RB250, other say on the RB1000.

Does anyone have correct information about this issue?

The transrotor TR9.1 is a modified RB300.
Modifications are:
1) No spring.
2) Better bearings.
3) Different counterweight.
4) Van Den Hul cable with no connections 'till the RCA's.
5) Nice silver painting.
Actually is a very nice tonearm with the main issues (spring and bearings) of the classic Rega RB300 settled.