Anyone familiar w/ these? They're used by Boston's MBTA and come in four odd wattages: 56, 101, 151 (rare) & 201 (latter comes in both clear & frosted; all others frosted only). Most of the old lights in the stations have been replaced w/ fluorescent or HID, but some incandescent fixtures can still be found in a few as well as in sections of the subway tunnels. Another common use was a fabricated setup of 5 cleat sockets, w/ these lamps, mounted on a wooden backboard & wired in series for 600VDC (these were found quite often during construction).

I had an uncle who worked for the "T" back in the 80s & he used to bring home loads of these. So, he gave me samples of all 5 bulbs. Thought I still had some NOS's packed away, but can't find 'em to date. If I remember correctly: the stamp has "Sylvania" in a arc at the top; "Street" over "Railway" in the center; then "*Wattage* 120V 6000Hrs" in an arc at the bottom.

Note: Somewhere, I also think I have some NOS Sylvania "Traffic Signal" bulbs. These are the same shape as the 56w SR, but are clear & come in 69w & 116w varieties. I remember these being marked, "Base Down or Horiz." They would actually shatter if operated base up (as I once found out to my dismay).

Madness:

I bought some Philips Street Railway bulbs at a surplus store about 8 years ago.  They are not that old because they are made in Mexico but I couldn't find them in any catalog.  Dave "Silverliner" told me they are vacuum lamps as opposed to gas-filled.  Mine are A21 short neck lamps (just like yours).  They are the same size as the 69 watt traffic signal bulbs.

I don't know why a vacuum lamp was used for railway applications.  Mine are acid-etched frosted, 56 watts, 130 v.  They burn very dimly.  Since they are vacuum, they light up slowly (luminescence) and dim slowly (nigrescence) when turned off.  I have mine in a early 1900s vintage ceiling chandelier.  The bulbs blacken really badly as they age.

I bought about 10 of them and I think all are still working.  I've lost some over the years.

Take care.

Alex (Lumalux)

The Street Railway lamps were used in electric streetcars that ran on 600v dc.  the lights in the cars were ran 5 bulbs in series. 120v times 5 bulbs equals 600V.   Now when a lightbulb runs on DC, when the filament breaks, it creates an arc.  also, remember in the early days of streetcars, the lights were uncovered, just bare bulb. if the envelope had trace amounts of gas, when the filament broke and arced, it could cause a small explosion and then the bulb would explode. by having the envelope in a total vacumn, you minimised the chances of an explosion. and the vacumn also helped to extinguish the arc. The bases of SR bulbs were also heavily insulated, so the arc couldnt travel to some uninsulated pocket in the base and fester, and eventually start a fire in the base of the bulb.