Hi All,
Looking at it, there have been four periods of significant change since TOC assumed its modern routing in 1870.
1) 1866-1870 When Old Tom built the 1st and 18th Greens
2) 1904-1905 Added 200 yards, 13 bunkers, returfed or relaid 7 Greens
3) 1924-1936 Expanded the 2nd green to the right, raised the hollow in front of the 6th green, removed 2 bunkers, added 7 new tees
4) 2012-2014 3 bunkers removed, 3 bunkers moved, 2 bunkers added, 1 bunker adjusted, part of 11th green adjusted, some 'broken ground' created by 3 greens.
Old Tom was on-hand for the first works, no-one in particular associated with the works in the second and third phases (but Harry Colt was on the R&A Greens Committee from 1924-1928), and Martin Hawtree for the current phase.
Looking at the works, the first phase was the most significant as it gave us the routing we now have. The second most significant phase took place in 1904-1905, and then maybe the current phase is the third most significant but it is pretty even with the 1924-1936 period.
Other works have taken place in between these periods, such as the addition of new tees, or the removal or addition of some bunkers, but the majority of works do seem to be in concentrated periods.
Hope this helps give some historical context for the current period.
regards,
Scott