Should professionally restored look like this?
 

Don't know Papa. The following one was claimed being professionally restored. Although it's hard to tell a gun from a single one-side picture, it is surprising, isn't it?

What's restored.... from this picture? Bore?

http://www.gregmartinauctions.com/Auctions/AuctionLot.aspx?LotID=23481

Probably "touched up" here and there.

is that a Luger grip fitted to the gun?

No. On Luger, the magazine release button is on the edge of the wood panel. On Nambu, the button goes through a hole.

Papa Nambu is a pretty pistol IMO. The size is right as well. In contrast, Baby is too small, and Type 14 is too much simplified. But that's personal taste, not useful on ID a particular instance's rework status.

The grip does not fit the gun well. Anything else?

restored?
 

Way too much straw on the trigger for such an old Nambu with all of that pitting. -B.