A tinned wire and a couple of double lugs

Here is a great example of tinned wires where you can see the tinning scrapped off exposing the copper below.

As for double lugging of neutrals (grounded conductors), they need to land on a single termination.

The requirement for neutrals was enforced in the past by the manufacturer markings and by NEC 110.3(B). Clause 12.3.10 of UL 67 (Panelboards) states, “An individual terminal shall be provided for the connection of each branch-circuit neutral conductor.”

NEC- 408.41 Grounded (Neutral) Conductor Terminations

Each grounded (neutral) conductor within the panelboard must terminate in an individual terminal.

From Mike Holt-

“If two grounded (neutral) conductors were connected to the same terminal, and someone removed one of them, the other might unintentionally be removed as well. If that happens to the grounded (neutral) conductor of a multiwire circuit, it could result in excessive line-to-neutral voltage for one of the circuits.”

Great link from Square D-

http://ecatalog.squared.com/pubs/Ele...0100DB0705.pdf