Hello again, Craig...
The more recent date-list in the Bobba book on page 207 list your serial # 28740 as being made in 1929 and not 1928. 1,401 pistols were made in 1929. 870 were made in 1928. Serial number 28340-28341 was the cut over from Year 1928 to 1929.
Regards,
Pete... <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />