I’m changing the load panel in a mobile home with additions to gain additional circuits.
Outside a few feet from home is the service pole with meter and a 100 amp disconnect.
I became concerned about the entrance wire because it is a fine stranded wire like automotive battery cables or like welding equipment wiring. The picture shows the work in progress and it is complete now but I wonder if this type wire is anything to be concerned about especially since I will be adding to the load draw with a central heat pump.
In the red square you can sort of see the fine strands that the entrance wire has. I can’t get better pictures until I return to this vacation home.
To clarify I was expecting the wire to be stranded like this
But what I have is very similar to this
Edit:
Returned and pulled old wire out. It was in a heavy rubber jacket that had writing on it indicating it was mobile home wire like one uses for a camper at at campground.
It stated it was for 50 amps.
. 
Replaced with #1 copper wire on hots and neutral and #3 copper on ground.
Best Answer
A terminal problem
Beyond the potential labeling/marking (or lack thereof) issues with this wire, there is a serious problem with this setup: equipment terminal lugs are not suited for fine stranded wire (anything finer than what UL calls Class C stranding) unless the equipment is specifically listed for use with specific fine strandings, which is not true for light duty loadcenters.
As a result, what we have right now is a 110.3 violation of the loadcenter's listing and labeling, atop anything else that's going on with the wire itself. Given that the wire appears to be in conduit, simply replacing the run with the correct stuff is the best option, as that will cure any issues with labeling/marking as well, and also gives you the chance to adjust conductor sizing as-needed.