You ask several questions so I will try and answer what I know. How do I know if the connections are proper, this is a tough one  , but they look similar to what we used back then the problem is if you cut them open to verify the crimp lug they are no longer sealed. When the tube shrank down it made the stamp hard to read but there should be a stamp on the shrink tube.

Is the wiring safe, if properly terminated it is safe since there were not many devices (breakers, receptacles and switches) that were compatible pigtailing with a crimp was one method the ones I used had anti oxide compound in the crimp-lug held in by a pice of cellophane, then you slid the sleeve of shrink wrap and heated it to seal the connection. You may be able to read the stamp on a few but most of the time it was not legible after shrinking.

The grounds it looks like there are a bunch under 1 screw. Their are a few panels that are listed for up to 3 ground wires under 1 screw but their looks to be more than that there.

The age of the wire, that one is tough but you should find the date stamped on the wire with the manufactures name if you can find that it was when the wire was made.

It looks like a quality install with the possible exception of two many grounds under 1 screw.

The only problems I have had with aluminum wire that was properly terminated was on remodels the aluminum breaks easily where copper can be flexed many more times without failure.

Aluminum wire is no longer used for branch circuits but is used for feeders most of the time. The alloy has changed over the years but when aluminum wire is used with proper splices and or al/cu listed devices it is safe.

You ask several questions so I will try and answer what I know. How do I know if the connections are proper? This is a tough one, but they look similar to what we used back then. The problem is if you cut them open to verify the crimp lug they are no longer sealed. When the tube shrank down it made the stamp hard to read but there should be a stamp on the shrink tube.

Is the wiring safe? If properly terminated it is safe. Since there were not many devices (breakers, receptacles and switches) that were compatible, pigtailing with a crimp was one method. The ones I used had anti oxide compound in the crimp-lug held in by a piece of cellophane, then you slid the sleeve of shrink wrap and heated it to seal the connection. You may be able to read the stamp on a few but most of the time it was not legible after shrinking.

The grounds it looks like there are a bunch under 1 screw. Their are a few panels that are listed for up to 3 ground wires under 1 screw but their looks to be more than that there.

The age of the wire? That one is tough but you should find the date stamped on the wire with the manufactures name.

It looks like a quality install with the possible exception of too many grounds under 1 screw.

The only problems I have had with aluminum wire that was properly terminated was during remodels. The aluminum breaks easily when flexed, whereas copper can be flexed many more times without failure.

Aluminum wire is no longer used for branch circuits but is used for feeders most of the time. The alloy has changed over the years but when aluminum wire is used with proper splices and or al/cu listed devices it is safe.