These replacement Sofitte or small tubular lamps/bulbs were 
specially used by Mueller in their "Seiffen Village" 7 Candle 
Arch - Schwibboggen.  (They may have been used by other 
manufacturers as well.)

The arch has 7 exposed candle bulbs on the top outside of the 
arch but also has 5 lit buildings, with these small festoon or 
sofitte 3w/12v lamps used within each buildings for illumination.

Check the voltage and wattage marks 
carefully on the base of your existing bulbs.

Length approximately 28-30mm 
Diameter approximately 8-10mm 
3Watts - 12Volts