Are you sure it's 10B? On my screen, that looks like 12B with some grime on the tag...... compare with the 2 in the interior trim code directly above.
But as you've got access to the car in person, if it's definitely 10B, perhaps it's a late 1969 build? Does the car still have a Norwood VIN, or was it assigned a Swiss VIN on homologation?