RF Si transistor identification

[alan.bain]

I'm trying to identify the active device in a 3.6GHz DRO oscillator found in an E444X series Spectrum analyser.  There is even a write up of a very similar oscillator design in Microwave Journal
https://www.microwavejournal.com/articles/11889-high-tuning-sensitivity-dielectric-resonator-oscillator-from-optimization-of-dielectric-resonator-te-sub-01-948-sub-mode

which sadly doesn't say what the device is. It is marked 420 with a dot see photo to the left of the dielectric ring.

[RoGeorge]

Could it be BFP420, or equivalent?

[alan.bain]

Thanksl that was a useful starting point. I don't think it is right, but it led me to the Avago AT-42086 which has a specification which looks like it might work and some pictures of them (on eBay!) show the marking of 420.

[fzabkar]

AT-42085 has the same marking:

https://www3.nd.edu/~hscdlab/pages/courses/microwaves/labs/AT42085.pdf

https://ja.aliexpress.com/w/wholesale-AT%2525252d42085.html (photos)