E013 translates to a the 13th week of 1990 in Singapore. Let me check myoldmac's database to make sure.

Edit: Yep, here it is:

Manufactured in: E => Singapore

Year of production: 1990

Week of production: 13

Production number: 11C => 1202

Modell ID: M5390 => unknown Mac

Your unknown Mac was the 1202th Mac manufactured during the 13th week of 1990 in Singapore.