You call  this game the Amsterdam Attack, but 1.e3 on his own is called the " Van 't Kruijs Opening " , named after Maarten van 't Kruijs, once, in 1878 the in-official Dutch Chess Champion.

In 1861 he played Adolf Anderssen in Amsterdam and opened with 1.a3, the same as Anderssen did against Morphy in 1858. 

Like 1.a3, 1.c3 and 1.h3 you leave your opponent the choice of the opening ; 1.d3 was often played by GM Mieses and 1.f3 by Barnes ; at 1.b3 and 1.g3 you intent to fianchet your bishop.

Karpov once thought it was an insult to play 1.a3 ( but lost, with black, that game ! )

Why did you post this opening ? Are serious games played with 1.a3 ?

Van 't Kruijs was ( in 1848-1851 ) leader of the Amsterdam Chess Club Philidor in games they played against London, with even Daniel Harrwitz as consultant.

I hope this post will be continued !  Regards, RomyGer, Holland.