Single pipe steam reverse engineering mystery

1Matthias

EDIT: Apologies about the length of this post. Seemed smaller in the editor.
So, got called out to a job the other day, new client with a steam system. Single pipe, beautifully unmodified since the early 40s at the latest. 75%+ of the system is original, and most of the 25% is acceptably well done. However, there are some oddities. There are 2 mains heading out from the boiler room, one which snakes around the basement clockwise (2"), one counterclockwise(3"). The counterclockwise main has what appears to be a kind of drip splitting off the bottom of the main almost immediately after leaving the boiler room. The "drip" (Better term may be an secondary main) continues around the outside of the basement counterclockwise, and actually supplies 3 or 4 radiators with steam. The main has what appears to have been a true drip off the bottom of the main further on at a reduction from 3" pipe to 2", which has since been plugged. The clockwise main supplies several radiators with steam, however two are supplied from the side of the main, with no pitch on the runouts. Oddly, these radiators are perfectly well behaved, with nary a single clang nor fountains from the vents. Near the center of the house, all the mains, including the secondary, converge in a small area, and drop to a wet return. The secondary one has no main vent, and the vents on the other two are either leaking or undersized (This will be fixed). Oddly enough, the underground return seems to continue under the concrete past where it exits the boiler room, almost to the junction of the first main and the "secondary main".

I have created an album with some photos of the setup, as well as relevant details, and can procure more if needed. https://imgur.com/a/aSJPbMp

I obviously have a couple of questions about this setup. First and foremost, is an additional main vent on the "secondary main" needed? I suspect so, but want to confirm. Second, would it be necessary to replace the drip off the bottom of the 3" main? Seems odd to me that it was removed, although as far as I can tell, it is not causing an issue, besides potentially holding water in the main. Third, does anyone recognize the radiators in the photos? I am not seeing them in EDR, nor have I seen any markings on them to indicate a maker. Most are this style(https://i.imgur.com/RPwDJSr.jpg), with three AmRadCo Cortos, and one 5 section made by a "NYR". I would like to tabulate the connected EDR of the system to determine if the boiler is oversized prior to making further changes to the system. Any input is welcome.