Maybe european sockets are different?
The British/European bulbs are the same fitting as American physically. The only notable differences between them and the #1157 are:
1. The silver-colored base instead of plain brass.
2. "E" approval marks instead of SAE/DOT.
3. The filaments are rated slightly lower than U.S. bulbs -- 21 and 5 watts
Actually that last point is interesting because this Gerlux bulb is stamped 21/4 watts. I've never seen that before. Very strange.
