Slightly off-topic, but I have an old GE 1960 miniature lamp catalogue here which I checked out, and its not listed there either.
18-24V does sound strange for automotive use, but in the UK the majority of early auto bulbs I have come across tend to be marked as suitable for 10-14V, possibly implying that voltage consistency at the lamp terminals wasn't all that good on early cars.
Perhaps 1145 was a type for old large buses and trucks or other 24V vehicles and it was known that for the length of wiring involved to the back of such a vehicle, you'd never get more than the 24V there. So maybe the lamps were marked with the typical voltage that might be experienced in such applications. Even today it is customary to mark automotive lamps with the voltage the car owner would expect to see, rather than what is actually delivered (certianly in Europe anyway). Halogen Headlamp bulbs here are all universally marked as being 12V, even though they are technically actually designed for 13.2V operation.
Anyway I no longer require this old GE catalogue and it attracted no interest when I put it up on Ebay last year, so if anyone on this forum can find a good home for it let me know!
James.