A recent excavation has revealed a dump of chalk, flint and building material immediately below the top soil. The CBM when compared to other Roman sites is remarkably similar. There is no other dating material amongst this dump
Can 19th century building material resemble Roman building material in shape and form? e.g are there 19th century variants of imbrex and tegula? Are there any good reference works which may help?The main things that looks like Roman building material are horseshoe field/land drains. These imbrex shaped suckers have had me on the hop a couple of times (especially small fragments where you can't get a good idea of the shape), but manufacturing methods and a very refined fabric normally give the game away - as would any 19th century copies of Roman roofing. Checking out 19th century trade/business directories may also help with this aspect.
Some useful Publications:
Harvey N, 1987. Fields, hedges and drains Shire Album 21
RCAHMS, 1993. Brick, Tile & Fireclay Industries in Scotland
There's also a super display of field drains at the Yorkshire Museum of Farming at Murton, just outside of York.
There's the outside possibility that it's 12th-13th century curved and flanged roof tile. See:
A G Vince, J E Pearce & K H Armitage 1981, Early medieval roof tiles from London, Antiq J, 61, 359-62
Garside-Neville S, 1995. 'Tile File - Curved and flanged medieval roof tile', Interim: Archaeology in York, Summer 1995, Vol 20, No2, 31-34
Or, in general, contact the Archaeological Ceramic Building Materials Group (firstname.lastname@example.org) for your friendly local CBM specialist)