Skirtings are surely a Victorian invention, at least as far as artisan's dwellings go, so historically accurate would probably mean none...... That's what the conservation at the local council told us a number of years back (house dated 1605 with late Georgian lean-to kitchen) and I have found no evidence to the contrary since that time. We ended up putting in a low 4in skirting with a Torus bead as being typical of this area in the early Victorian period - but then we were retaining the "original" Victorian 4-panel doors and architraves so we simply picked out something in keeping with the rest of the house.
At the end of the day skirting boards came in to protect the base of the plaster from furniture legs and plastered walls was definitely something only found in the dwellings of the waelthy until some time into the Industrial Revolution.
For anyone looking for a Victorian reference might I suggest "The Victorian House Book" by Robin Guild (Sheldrake Press ISBN 1 873329 39 3), first published in the late 1980s and reprinted several times. This bok contains lots of detail photographs and drawings and is useful if like me you have a Victorian house and you'd like to make sure the detailing is reasonably in keeping with the original features.
Scrit