Bruce, with the T-auger the hole depths may be irregular and not as smooth and clean. The holes of the machine will be true to square as well or I should saw consistently the same, they may all be out of square the same. This all bears on the ability to find a mistaken mortice, it does happen. This is providing the worker was using a machine with a depth stop and the bit was true, even then it would of been more consistent. This comes from my experience of using both and with the ease of the machine I find it much easier to bore all the holes. The T is slower and all one needs is to cut the end holes and maybe one in the center. I also see mortices with fewer holes to make up the mortice, suggesting a T-auger. The T-auger with the feed screw was developed around 1798. If the bore hole doesn't have a feed screw evident at least the tool used was pre 1800. Machines were developed in the later half of the 1800, is my understanding. A lot happened and quickly from the start of this country, and we are not done.

Just because a certain tool dating to a certain time is used doesn't pin point the construction date, there is overlap. I am still using a boring machine in the time of Hundiggers and chains. One needs to compile all the facts and then guess.

Tim