This part is a kind of semiconductor called BDY25.

Function of this product has Bipolar NPN Device.

Manufacturers : Seme LAB

Image and pinout :

Some of the text within the PDF file :

BDY25 Dimensions in mm (inches). 25.15 (0.99) 26.67 (1.05) 10.67 (0.42) 11.18 (0.44) 1.52 (0.06) 3.43 (0.135) 6.35 (0.25) 9.15 (0.36) Bipolar NPN Device in a Hermetically sealed TO3 Metal Package. 38.61 (1.52) 39.12 (1.54) 0.97 (0.060) 1.10 (0.043) 29.9 (1.177) 30.4 (1.197) 22.23 (0.875) max. 16.64 (0.655) 17.15 (0.675) 1 2 Bipolar NPN Device. VCEO = 140V 3 (case) 3.84 (0.151) 4.09 (0.161) 7.92 (0.312) 12.70 (0.50) IC = 6A All Semelab hermetically sealed products can be processed in accordance with the requirements of BS, CECC and JAN, JANTX, JANTXV and JANS specifications. TO3 (TO204AA) PINOUTS 1 – Base 2 – Emitter Case - Collector Parameter VCEO* IC(CONT) hFE ft PD Test Conditions Min. Typ. Max. 140 6 Units V A Hz @ 4/2 (VCE / IC) 75 10M 180 85 W * Maximum [ ... ]

BDY25 PDF Datasheet Download