Here we have an Osram U52 DIRECTLY HEATED TAPE FILAMENT rectifier manufactured by Osram at their Hammersmith UK factory.
This device carries a white inked cartouche which list the factory code, KB/Z, the type notation CV575 - which denotes a military high grade device and the date code HC which corresponds to March 1953, the classic U52 envelope is tight to the trademark rounded black low loss micanol base and a small amount of loose valve cement is trapped inside.
Highly sought after not just for the impressive current delivery performance but for it's extreme musicality and deep bass extension in hifi applications this is a nice lot indeed. Even more so as it's in the delicious bulbous envelope presentatiion which not only enhances sound quality but looks wonderful. . No wonder all the high end magazines rave about these beauties.
The valve shows excellent bright getter and has the inverted cup getter pan situated down by the glass pinch. However, more importantly, both test as EXCELLENT using my Avo VCM163 valve tester.
Device test data: Ia = 120.0mA for both diode sections
Device specification 120mA delivery for both diode sections. So you can see we have 100% emission from this beautiful device.