Playing At Archaeology

Dig down anywhere in my mother's front garden and you hit a layer of building rubble- brick, stone, slate, glass, metal. I can only guess at what it represents. Am I perhaps looking at the rough and ready surface of a buried farmyard? 

I've been prospecting out there with my metal detector- working my way along the edge of a flowerbed. I haven't got very far yet because the second time the detector went beep I found I'd lucked onto a big cache of large metallic objects- and I've been digging in the one spot ever since.  First up was a wedge shaped item which- when cleaned- turned into a rectangular piece of steel plate with holes in it and boltheads still attached. That was yesterday's find. This morning I scanned the diggings again and I was still getting strong responses so I dug some more and out came a brick-sized lump- which looks agricultural- but I'll need to remove the accretions before I can be sure of its shape. I scanned again and the machine is still beeping. It's like there's a whole tractor down there.  I've exposed the edge of whatever the new thing is- and tested it with a magnet to make sure its metal-  but extracting it can wait until tomorrow.