blue 6V Bosch RKLE 90H beacon lamp

Rare Bosch RKLE 90H lamp with blue lens in used condition. I put 6 Volt on the lamp and it rotates but the bulb does not burn. I replaced the bulb with a new old stock 6V bulb and still the bulb does not burn. While rotating, it is quite noisy, possible because of the cogwheel drive. The blue lens has one crack (see last 3 photos) but you can still use the lens. The lens is stamped with "B1031, 8 785 510 050". The badge is stamped with "BOSCH RKLE 90H Blau, 7782300207, Glühlampe H1 6V 55W, Eisemann GmbH Stuttgart Germany, B1031, 71226, 21Bl" and the motor is stamped with "6V". Made in Germany.