Canadian quarter 2003

have a Canadian quarter from 2003, one with the old Queen looking right, without a thing on her head. Another Canadian quarter from 2003 but with the Queen from 2002 coins, without the crown on her head. Is this an error?

If you mean one of these N#377368 and one of these N#326 then no, not an error. 2003 was the change over from the third portrait to the fourth portrait.

No. Sounds just like 3rd and 4th portrait issues.

2003 was the year the portrait changed from the third to the fourth, both effigies were produced in the same year as with the 2015 UK issues