28-09-2019, 11:51 AM
This rung a bell with me so I had a quick look. Not much to add as I have five of these but I have obviously used them in test circuits in the past as the numbers have largely rubbed off. They almost certainly came from Birketts. One of them is marked 'Plessey' . I have them stored in an old transistor box and labelled with gain (around 50) as measured some years ago. The leakage I have noted as zero so maybe Silicon, but not something I will dwell on.
Tracy
Tracy