I suspect that may have been a wartime repair. During WW2 techs often couldn't get the right parts and had to scab in whatever they could get. It looks to me like those 2 holes at the left had stud mount can caps, and since they are not grounded to the chassis, they would have had to have insulated mountings. That works out to two ungrounded terminals per cap.
I wonder what the third hole is for? On the schematic, there is a 1mfd capacitor, or maybe 0.1. If it was .1, it could have been electrolytic, and it might have gone in the third hole. This cap had it's positive terminal grounded, so it would have also been insulated from the chassis. That ground strap from the chassis could have gone to the positive lead.
When I am having trouble reading a difficult schematic, sometimes it helps to draw it out in a more orderly fashion. I tried that with yours and this is what I came up with.
There are several screwy things going on here. First of all, the field is on the negative side of the power supply. This was sometimes done in the old days so the field didn't have to withstand B+ voltage. Second, the center tap of the power transformer is not connected to the chassis. This was done to develop bias voltage for the tubes. It's strange because the chassis is not the most negative part of the power supply.
The taps on that schematic are, starting at the top:
B+ (probably 250-300 volts or so)
B- (chassis)
Bias1 (negative voltage)
Bias2 (more negative)
Bias3 (even more negative)
Here's how I would approach it. I would solder a long terminal strip below the chassis where those holes are. You will need at least 6 terminals, 5 of which are NOT grounded. Technically you could get by with less, but thats how many there were probably originally when the old caps were there. (This is assuming the 1uf was also a can. If it wasn't, then four terminals, all not grounded).
I would start at the power cord and work my way toward the tubes. You should be able to trace the wiring through the switch, to the .02 line filters, which you should replace with modern safety caps, to the primary of the transformer. OK, now theres 2 transformer leads you don't have to worry about. On the other side, 2 wires will be for the 6.3 volt filaments. That winding also powers the pilot lights. One side is grounded. Trace to the pilot lights. Theres another two wires you can forget.
Whats left now is the 5v rectifier tube winding, and the high-voltage winding, which is center tapped. 5 wires in all. Probably the five volt winding (2 wires) will be one color, and the HV winding (3 wires) another color. The center tap of the HV will have a black stripe or something.
Now look up the pinout of the 5y3. You can get it at
http://www.nj7p.org/. Here it is:
On an octal tube, looking at it from the bottom, with the key slot down, pin 1 is to the left of the key slot. The numbers count clockwise from there. You are looking for pin 4 and 6. These are the high voltage winding, and they should connect to these pins and nothing else. Found them? Good. Theres 2 more wires you can ignore.
Now find pin 2 and 8. These are the rectifier filament pins. there should be wires connected to these pins from the 5v winding on the power trans. One of them has other stuff connected to it. The one with other stuff connected is the highest positive DC voltage in the chassis. Note. where it is. Ignore the other wire.
At this point, there should be only one power transformer wire left. This is the HV center tap, and is the most negative DC point in the chassis. Note where it goes.
These two points we just identified originally had wires that went to the first capacitor. You can probably identify which hole it was in. Put a terminal strip there, and connect the wires to 2 insulated terminals. Put an 8uf cap (450v oughta do it) across those terminals with the NEGATIVE side connected to the power transformer center tap, and the POSITIVE side to the wire that goes to either pin 2 or 8 of the 5y3 socket.
Ok, from there, the side connected to the NEGATIVE side of the capacitor should have a wire going to the speaker socket for the field. Connect it too.
Coming back from the speaker socket, it might get a little interesting. I'm gonna assume something here. Since the 220ohm, 32ohm, and 32(52?)ohm resistors are labeled 10a, 10b,and 10c on the original schematic, I think they were a single tapped resistor. It was probably a "candohm" crimped metal thing. I think I see it at the far left in your picture. They fail a lot, and also can short to ground, so check it carefully.
Working on that assumption, coming back from the speaker socket, the other field lead should come back to one end of the candohm. There will also be a resistor connected to the 6f6 grid. Moving down the candohm, the first tap we come to will be the other end of the 220 ohm section. There should be a wire heading over to where the one of the old caps was. Again, the length of the wire may tell you which hole. Mount a second 8uf@450 capacitor on 2 insulated lugs on the terminal strip. Connect this wire from the candohm to the negative side of the 8uf cap. Connected here also should be a 3 megohm resistor that goes to the grid cap of the 6q7. Connect the positive side of the second 8uf capacitor to the positive side of the first 8uf capacitor. Note that neither of these caps is connected to the chassis.
Next is the 1ufd cap, if it really is 1uf. I can't read it. It was probably mounted in a third hole I suppose, but you can probably skip adding the terminal strip for it. Electrically, it goes from the negative connection of the second 8uf capacitor to the chassis. The POSITIVE lead of the 1ufd goes to the CHASSIS.
Moving right down the candohm, the next tap should go to the cathode of the tuning eye, the cathode of the 6q7, and the volume control. The next tap is at the other end, and should be connected to the chassis.
Where the positive leads of the two 8uf caps connect together is the main b+ supply to the set. There should be a connection from there to the output transformer, connections to both IF transformers, the magic eye target pin, a 100k resistor to to the 6q7 plate, a 10k resistor to the 6c5 plate, and a 10k resistor to the 6k7 screen.
Good luck,
John