I'd take a punt on it being a FET of some sort, I'd be tracing out the circuit and deducing likely candidates.

The other alternatives are transistor or a diode (or 2).

Unless it's something very speccy or bespoke. I've run the markings and come up with nada.

A more general board view and function info could help, but as a first try, the * P is possibly a DAP2X2 switching diode (of the similar SOT 346 and not SOT 23 package) , * D could be a MRF577 npn RF transistor. S.M.

Thanks for your input. It turns out that it is what it's supposed to be: a BSS138, but the particular one I was looking at was faulty.

Both Fairchild and Zetec use SS as their component marking. Unfortunately Fairchild put another symbol in front of the code to indicate factory of manufacture; this symbol, a bar just happens to look too much like an I or a 1 as far as I'm concerned.

Like all these sorts of problems there was a lot of spurious information which led me to believe that either the components being fitted were wrong or from some unapproved manufacturer.

Thanks again.

Maybe one is a diode and the other a P-type Mosfet?

More probably it is VHF/UHF device; Power transistor.

Try to get old Japanese devices data book.

The OP knows what it should of been. He just wasn't sure that it was what had been fitted on the board.

It's now all sorted.