Line on right is large old woven "romex". Likely abandoned line to range.
center is conduit.
left is ground, which is clamped to an abandoned galvanized water line.

In fuse box, large old "romex" line is no longer attached to anything.

It appears that large ground line to water pipe, is attached to neutral bus.
4 old circuits have neutral going to bus.
The hot side of the 4 old circuits seem to be joined to 4 new hot lines in the conduit, headed to new breaker box via conduit.

Perhaps old conduit was main line in?
It appears to now carry 4 hot lines, one neutral, and a ground.

Odd to me that large ground line to water pipes attached to neutral, and there seems to be perhaps only one (blue) neutral tyeing to the new breaker box.
This might explain why the GFCI in the new bathroom is always tripped?

There seems to be a new ground line, in conduit, connecting to housing of this old fuse box, now jBox.