The Detroit Publishing Company postcard above is listed as having been published between 1898 and 1931, but I’d guess it’s from 1909. It shows Fort Ticonderoga after its initial restoration, which began in 1908 and was first opened to the public in 1909. Our current project there includes restoring part of that restoration.
In the postcard photo, the masonry looks very new, which is no surprise as the fort and its buildings were basically ruins when the restoration work began. The facing stone, as can be seen, is partially-finished rubble: stones of irregular sizes and shapes, squared off only as necessary to create reasonably-consistent joint widths. The bigger irregular stones at the base of the walls are original masonry that shows the extent of remaining ruins before the work.
The original versions of the fort – it was built in the mid-1750s, rebuilt around 1760, and repaired and/or rebuilt in the mid-1770s – were constructed by soldiers. It is quite likely that there were men among them with experience in construction, and particularly with masonry work. That said, the conditions for construction were less than ideal, building on an isolated site with local materials and limited tools. I doubt those walls were as sharp-edged and flat as those built 1908-1909. The construction was definitely different, at least in part, because the original walls were timber with stone facing, as opposed to the all-stone walls built in 1908. Some of the eighteenth-century walls might have been all-stone where they were rebuilt early on, but that was definitely not all of the perimeter.
The original fort was a temporary structure. I suspect that the various generals from the three armies that occupied the fort (French, British, and American) would have been shocked to hear that anyone cared about it 250 years later. The twentieth-century reconstruction was meant to be permanent and is itself a historic landmark in the history of the preservation movement in the US. In short, the fort deserves its restoration regardless of which era you feel is important.