Ask LiveJournal Electrician: light fixture maximum wattage?

We have this old swing-arm lamp that takes three position bulbs. The socket is stamped 250W 250V, but I can't tell if it's just describing the socket or if the wiring in the lamp itself is rated for 250W.

Most modern swing-arm lamps I've seen have a tag that says they're limited to 150W. I figured I'd ask around before I put a 250 watt bulb in it and started a fire. :)

Anyone have any thoughts?