Signs by which to recognize D1

[Daren Scot Wilson via Digitalmars-d-learn]

Someone looks at a chunk of D code of murky origin.  Possibly, it 
is old, maybe D1 not D2.  Inadequately commented, believe it or 
not, and not other information.

What are some easy to spot details in the syntax by which the 
onlooker can know it's D1 not D2?