Howdy
First off, any Triple Lock is worth investigating further.
It sounds like you have already answered my first question, it sounds like you have gotten it lettered. These days there are actually 2 separate requests for letters.
What used to be called a Factory Letter is these days called a Letter of Authenticity. I suspect that is what you have. These letters typically give a bit of history about the model of firearm, then tell specifics about yours such as the features it had when it shipped and where it shipped. Sometimes a Factory Letter will give more information, I have sometimes gotten a bit more than outlined above.
Now there is also Historical Letter. A different group takes the information from your Letter of Authenticity and searches digital files for any information pertaining to your revolver. They state up front that it is only for revolvers that shipped between 1920 and 1966. So yours may not be included. But perhaps there is information about the work done in 1929.
Here is a link to the site which lists both types of letters. It appears to me that if they don't find anything when you ask for the Historical Letter, you will not be charged anything.
http://www.swhistoricalfoundation.com/info.html
You could also post your question on the S&W Forum. There are some very knowledgeable folks there who may be able to shed some light on your questions.
This link should take you directly to the section relating to Hand Ejectors made between 1896 and 1961.
http://smith-wessonforum.com/s-w-hand-ejectors-1896-1961/?s=8968fd1810cbe3e2c42919ff9ddd0480
Lastly, I would be a bit reluctant to characterize the repairs done because something catastrophic happened to your Triple Lock. It could be a simple explanation of a lot of wear, or something similar.
If the cylinder blew up, the frame would most likely have been damaged.
From my standpoint, any Triple Lock is worth investigating further.
You are correct that when they first shipped in 1908 the Triple Lock was priced at $21. When the 44 Hand Ejector 2nd Model (without the third lock and without the large underbarrel lug) was introduced in 1915 because those features had been eliminated the price was reduced to $19. In those days, $2 was a significant amount of money. I just checked with an inflation calculator and it comes to $50.77 in 2020 dollars.