Eminar amps were made in High Street, Northcote, Melbourne, Australia in the 1970s. [Source: Oz Valve amps]
Dating Eminar amps
Based on the photos below it would appear that Eminar amps can be dated from the serial number (first 2 numbers are the year of production) and if you open it up the date of manufacture will be written in oil pen on the chassis.
Images Eminar valve amps eBay: