I don't think magnification is the problem, it's the visible detail remaining (or not remaining) on the coin.
It's definitely post 1279, and almost certainly London mint (the reverse pellet-side inscription reads, without too much imagination, CIVI TAS LON DON). But all I can see clearly on the obverse are some of the king's curly locks, bits of his crown and the end of the inscription: ...L DNS HYB +.
Unfortunately, narrowing down a specific type or variety requires a nice clear view of the portrait, and the beginning obverse inscription to be readable. I don't think either is going to be the case for this coin. Much of the first half of the obverse legend appears to be mostly off-flan on this coin, either through clipping or off-centre strike; probably the latter, since there doesn't seem to be a corresponding missing bit on the reverse.
To address the original question: for an unattributed (and in all likelihood unattributable) penny of the period, I couldn't justify paying that high a price.
