These alloy-junction transistors were manufactured at the National Institute of Telecommunications in 1557. A total of about 10,000 were produced, with little yield. The datasheet states that they were developed on the basis of a model TW transistor. After assembly, the transistors were measured and selected. The ones with good parameters remained properly marked, the ones with poor parameters remained unmarked and they were shown in the photos, and apparently one can find one somewhere at auctions. I even found a transistor datasheet. The typical reinforcement of functional items without markings from the collection is only 3 to 8, so it is small. Compared to mass-produced types, the housing is much larger.