Valve Timing

We are looking at 100-year old machinery: any timing marks (dots or scratches or anything else), should be treated with caution! Instead, I recommend turning to First Principles, as follows:-
Rotate the crankshaft till both pistons are at Top Dead Centre.
Without moving the crankshaft, mesh the camshaft pinion with the crankshaft pinion so that on one cylinder (it doesn't matter which), the inlet valve is just opening and the exhaust valve is just closing.
Rocking the crankshaft a few degrees back and forth will cause the valves and rockers of this cylinder to 'dance'. This dance should be very nearly symmetrical about Top Dead Centre of the pistons.
If it's not (see Association Newsletter No.1009 of May 2014, Second Paragraph!), advance (or retard) the cam pinion by one tooth at a time, relative to the crankshaft pinion, to obtain the best possible 'fit'. (With its 42 teeth, the incremental advance/retard of the cam pinion, per tooth, is about 8 1/2 degrees).
This will do the trick, as accurately as it's possible.