Very nice! I have one of these myself, which I found for like 5 bucks at a junk store, (one of the small, independent, locally owned ones that still accepts "hazardous" stuff like CRT televisions, vacuum tubes, ballasts, fluorescent tubes, HID lamps, etc. (And there's always an abundance of lighting stuff there it seems). I never did get mine lit since the HX-NPF ballast in an old yard blaster wouldn't light it (not enough OCV) but I just bought a proper M57 kit so hopefully that will change this spring).

Thanks! I found this one at a thrift store for $2.50

Nice! I have 4/6 of a case of these from 2000 as well. I got mine from school a few years ago. Never lit them though.

Now, Mike, what's that fraction once reduced?

Very funny... Actually now that I think about it, I have three of the six lamps, so 1/2- er- I mean 3/6 of a case.

Or 4/8, or 5/10, or 6/12, or 7/14, etc. etc. etc. Now challenge me with some algebra equation if you dare...

No, there's only six lamps originally.

OK, here you got! I just did this problem yesterday:

The length of a rectangular metal plate is 3.00 cm greater than twice the width. Find the dimensions of the metal plate if its area is 35.0 cm squared.

OK. Set the width equal to some variable, let's say W. Let's "name" the length as W+3. Now, knowing the area is 35, we can set it up as (w) (w+3) =35. Now distribute, so we have w^2+3w = 35. Now I'm ever so slightly confused. We could factor out a W, but then that just undoes the distribution. Now, believe it or not, I'm stuck. And my math seems to be way harder than yours.

These are the better lamps. The newer ED jacketed ones have a high failure rate.

Yeah Sylvania's BT MH lamps were one of the best on the market. I don't have any experience with the newer ones though. Does Sylvania still make the ED ones in the USA like the BT ones? Are the HPS lamps ED now too or are they still the oddball ET23.5 shape?

As far back as I remember, Sylvania's ED 23 1/2 HPS lamps were manufactured until I guess the mid 2000s.

The ET23.5 HPS lamps were made as late as 2014 but I don't know if they're still currently made. When did they switched to ED MH lamps? I've seen the BT ones until rather recently. The BT Mv lamps died by 2000. Sylvania was selling GE and Philips lamps under their own name between 1999 and the early-mid 2000s until they started making those ED-shape Chinese MV lamps (which ironically are second only to Eye Lighting as far as quality goes).

Sylvania still makes the ET shape for their 100w mercs and lower wattage HPS lamps. Also, the local Menards just restocked the metal halide shelf with new Feb 2017 lamps and some were BT shaped, but not all of them.