Hi everyone, I am in need of some assistance in gaining information on a particular bulb. I'd like to learn more about it and hopefully someone can help me. It was installed as part of a lighting fixture on a large oak tree I had taken down. The tree stood for about 100 years. When I found the bulb I wiped it down and did a little research but was eventually stumped. It appears to be a Philips Lifeguard 175W mercury bulb. However, I am curious approximately when it might have been manufactured and other technical details anyone could share. I've included some pictures here. Any help is appreciated.
Thanks in advance!

This is a nice and well made lamp, with plenty of life left. I'm curious when this lamp was made too. Now that I've bumped it maybe an expert here might reply.

Could do with seeing the etch more clearly, there will be a date code on there somewhere. I think I can see H3 on there, which is August 1983 if it's using the usual Philips code.

Technical specs are easy, this one will be electrically identical.

Hope this helps 

The visable H3 is the beginning of the lamp code, which in this case is H39KB-175. Need a better picture of the etch to determine manufacturing date.

Its definitely from the 80s though, as philips abandoned the BT28 shaped lamps by the early 90s.

@ BT25 - Ah, that makes sense, shows how much I know   

@RadiantMV: Philips discontinued the BT28 in 1988...
@Rommie: You're off the hook...I'm not expecting you to be proficient with US made lamps.
To the OP: If the etch has only Philips mentioned and no Westinghouse, then it's either made in 1986, or 1987.