I think you're talking about my 1974 OSSA Explorer 250. It's the trials bike (I also have an MAR 250, made 2 months before the Explorer), but with a bigger fuel tank and a more substantial seat. Headlight, tail/brakelight, and speedometer down on the front fork leg.
For really gnarly deep woods, you'd probably want one of the 90/100 Jappers such as the little Kawasaki 100 - you can carry these out of trouble, but they take you forever to get to the woods. My Explorer will do +/-130kph flat out - uncomfortably and scarily, but it'll do it.
Honda XL1000V, Suzuki DR650, Adventure Royal Enfield, OSSA Explorer, first model XL250, 9 other offroad, road, and roadrace bikes