Ted, with all due respect I do not think that the lunette is an indication of smokeless proofing.
The lunette was built until 1909. The first Nitro proof was made in 1897.
This is indicated by a "R" after the model number i.e. 4R.
R stands for "renforce" (reinforced action). Of course the proof marks will show this with the crown over PJ, PS, PM or PT.
Best regards,
WC