Up to now, I have seen a two number date code on all Westinghouse lamps from at least the 70's through the early 80's until Philips took over...then it was the letter-number combo. Well, on ebay here, this looks like a late 70's to early 80's Westy with Philips date code: N9 which would imply '89? But BT was gone by '89 along with Westinghouse logo. Any ideas?

Nothing unusual Don. The last three months of the year use letter codes. O for October, N for November, and X for December. Yours is indeed from 11/79.