So heres an interesting one, I was at my electrical counter today and noticed some large ballasts on display that ive never seen before, of course I had to have a look, they were the newer GE F-Can metal halide ballasts in 100w, 150w, 250w and 400w. Initially I thought these were electronic until I picked one up, then saw "CWA". These were all manufactured this past July and I guess GE discontinued the entire line of their old F-Can halides (black case) and these new white ones conform to some energy efficiency program for probe-start MH. Btw, these things are EXPENSIVE, double the price of the old GE models, the 400w size goes for $300.00 each!! Who in the right mind would pay $300 for a 400w halide ballast when core and coil kits are $50? Anyways the dealer I always order from agreed to sell me ONE at cost so I took a 400w. After doing some testing on it I found its open circuit voltage is 960v! Far above normal probe start OCV. The sticker on the ballast claims OCV of only 283v. I connected it to a pulse start lamp (Venture Uni-form Pulse) and it fired after about 5 seconds! Then I took a 400w Sylvania probe start lamp that is always a hard-starter on any other ballasts and it fired the second I switched it on. Interestingly enough the label also states "insulate red lamp lead for 1000v". There isn't supposed to be an ignitor in this ballast so how is this possible??? Some pulse start ive got wont fire, but alot of them do. Is this a probe or pulse start ballast?

Btw this thing is huge, normal claw hammer behind it for reference

My guess is that it is a standard probe start ballast with a high OCV. Maybe somehow the higher voltage makes it more efficient?

The ballast state M59, meaning 400W probe-start MH lamp. Also its nominal OCV is 282V, typical OCV for probe-start MH lamps.
If this would be a pulse start MH ballast, it would have an OCV of 240V, like MV and HPS ballasts.
Also, lower loss magnetic ballasts, are larger than higher loss magnetic ballasts.

Dor, thats what I thought. But the digital multimeter reads 960v until the lamp strikes which then it instantly drops to normal operating voltage. I tested this numerous times. They must've employed some sort of soft-start ignition circuit that only provides 1/4 of the typical 4kv ignitor, possibly for extending lamp life (old worn lamps will ignite longer) im not sure. One thing I do know is that lamps warm up much faster on this ballast, I used the same 400w lamp on this ballast and an Advance M59 (71A6051), the lamp reached full output on the GE F-can in almost half the time it took the Advance. At full power, the Advance reads 448w (quite typical), the GE reads 411w. Of course with this higher OCV restrike time is cut down considerably too.

OCV of 960V is also suitable for probe-start MH lamps, as in Europe, these lamps are used with MV reactors and 750V-1KV two wires parallel ignitor amyway.
However, you say that with this ballast, probe-start MH lamps have shorter hot restrike than with normal M59 ANSI ballasts, having OCV of 310V. But probe-start MH lamps have a bi-metal that short-circuits the starting probe after lamp run-up, so the starting electrode, receives no voltage, until that bi-metal opens. So with this ballast, probe-start MH lamps hot restrikes without an appearance of the aux discharge (Meaning as soon as that bi-metal opens)?

Yes, there is a discharge between the starting probe and the adjacent main electrode about 20-30 seconds before restrike, its just happens about 5 minutes sooner than it should for a probe start M59 system (due to the ~1Kv im guessing). What I really want to know is where the 960v is coming from, a tap off the transformer, or a component separate from it and the cap? Also the potting compound isnt the tar like fill thats traditionally been used, its that rock solid epoxy resin stuff, theres a small part of it exposed near the leads

The high OCV reached in an old fashion (just by turn ratio) does mean high losses, thgerefore classic designs have the OCV just barely the minimum level the lamps need. And that won't be the reason for that high voltage with an intentionally high efficiency ballast.
I would rather guess for lower intrinsic OCV (around 200V or even less), but boosted by a HF ignitor.
And there I would really guess for some kind of HF oscillator circuit, not just pulses. That is, because the higher voltage is needed not only for ignition, but for the complete glow discharge time, till the electrodes heat up to the operating temperature.

As the higher voltage generated by the extra HF ignitor does not require the high turns ratio, it does not bring the extra losses when increasing that voltage as in the classic design. So the reason for using limited OCV (the increased losses during normal operation) is gone, so they really went all the way up to the lamp's limit, to make the ignition reliable.

Eltam manufacturing similar all in one control gear (Reactor ballast + capacitor + ES-PI 1000 ignitor), for HPS and pulse-start MH lamps, from 35W to 150W. However, they looks different than the one BlueHalide posted: http://www.eltam-eh.com/Products/182/220V-240V%2C_35W-150W .