I've been watching this one for a couple of days. Quite amusing. If you look at a Coaling Scuttle it will generally have 2 holes in it.
The "T" bar handle will have 2 prongs. Prongs fit holes. Turn "T" bar and loosen or tighten. Oddly enough, they are still in use today. The "flush-mounted" refuelling points on some RFAs still have screwed in cover plates that neen this sort of "spanner".
But there is anther sort of "scuttle key". I presume the subject is about "coaling scuttles" and not about "scuttles" (i.e. "Portholes"). Different thngs altogether. BY.