Hi and welcome. Looks to be a later frame and although rusty, appears sound enough. Teeth on the sprocket will give an indication of a previous life...49 suggests a sidecar bike, check for a pulled frame as a start.
Came with a clean spare set of cases? Check for matching numbers under the dynamo mount, you may also find dates stamped on each crankcase half.
Do not threaten it with that chisel, heat is a better tool than the violence employed by some miscreants. Dig out the Cycle thread taps and dies, Whitworth spanners and the penetrating oil......
Swarfy.
PS Looks to be a luxury working environment!!