Does "Suitable for use in open fixtures" mean not suitable for closed?
I think the "660W 250V" reference is to some specific part of the fixture - perhaps the socket. I find it highly unlikely that a US residential fully enclosed fixture would be rated (a) for 660W - that is way too much power == heat and (b) 250V - the ratings for lighting fixtures (as opposed to switches, timers, etc.) is typically for 120V.

Based on the info at Home Depot for this bulb, this appears to be designed for "table lamp, sconce, vanity, pendant" - all of them open. I wouldn't put a 40W or 60W (and this is in between) bulb into a totally enclosed fixture like you describe - that just does not sound like a good idea. In a very quick read of the page, I didn't see a reference to a full manual, but it sounds like "open" is code for "not closed".

In any case, 43W dimmable incandescent makes no sense at all. Incandescent bulbs are the cheapest in up-front cost. But it doesn't cost much these days to get dimmable LEDs. For example, these Cree bulbs also from Home Depot cost a little more but give you:


MUCH lower power consumption - 10W vs. 43W
MUCH longer life
More light - 815 lumens vs. 600 lumens


and specifically list enclosed fixtures.

About the only scenario (a bit of a stretch) where it would still make sense to worry only about the up-front cost and not about energy cost or replacement cost (both vastly lower with decent LED bulbs than with incandescent bulbs - lower energy costs and fewer replacements) is a builder who wants to put in everything as cheap as possible for profit. (And even then, putting LED bulbs everywhere would let the builder advertise the "energy efficient home").