Inspired by the above and needing a rip tenon of suitable size and pitch I won this
http://www.ebay.com/itm/220963966162?ss ... 500wt_1378
At 14" and 11 tip it just needs filing to rip
A little research revealed the likely saw maker
STRAW, William LONDON
2 (3,4) Wellington place, Greenwich road 1870-1878
34 Greenwich Road 1882
which dates it rather nicely.
No doubt he was in business to supply the local ship building industry which flourished there at the time. It looks a quality saw and it is very satisfying to know a bit of the history. At £11.78 it seems a bargain. It looks like Derbyshire may be it farthest trip North (so far).