On 8 Sep, 11:37, bof wrote:

So what was it doing in my loft then?

It may be a surface plate, if the other side shows signs of maching
or lapping to make it very flat. If it is, it would probably have some
value, which is the only reason I can think of for someone keeping it.
It doesn't show any sign of rust, so it is more likely cast iron.

Otherwise it fairly worthless scrap.