This barretter carries the Osram name and could be their Type 251. However, it also carries the STV/Telefunken Type 85-255V0.08A and the Telefunken logo. Clearly this is a Stabilovolt (STV trade name) barretter made in Germany and re-branded as Osram.
See AlsoH85-255/80 for the STV labelled direct equivalent and HU8525 for a similar Barretter.
One side of the envelope carries the Osram brand and the rating of 85-255 Volts at 0.08 or 80 mA.
The other side carries the BAL716 identification to show it was made to the German Luftwaffe standard and inspected at that particular office. The lettering above is RLM Eigentum, equating to property of the Air Ministry.
Also etched into the glass is the Telefunken logo.
The three pins of the B4 base. Pin 2 is missing.
The fine coiled iron wire that forms the resistance element. The envelope has a hydrogen filling.
The wide glass tube envelope is 40 mm in diameter, and excluding the B4 base pins is 163 mm tall.
References: Observation, 1043 & 3002. Type 85-255V0.08A was first introduced in 1939. See also1939 adverts.
