www.ebay.co.uk/itm/VINTAGE-LIVE-STEAM-2-5-INCH-GAUGE-0-64-0-LOCO-6-WHEEL-TENDER/273796178957?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649
it is not a Drummond LSWR class 700 black motor but looks closer to the LBSC C2X class of loco. Some of them had double domes in later life. See the web link below to show some pictures of how the locos changed appearances over the years.
http://www.semgonline.com/steam/c2-c2x_01.html
Mark