Some people call them "Mexican Standard" which is probably a better, more descriptive way to refer to them.These will have 'Made in Mexico' and a serial number right on the of the headstock (except for certain vintage re-issue and deluxe models).
The "American Standard/Series" will have a serial number (S/N) that will be found on the back of the headstock.
Those made in the 90's will have an S/N that starts with 'Nx' and those made in the 2000's will have S/N's that start with 'Zx', where 'x' equals the last number of the model year.
Post a picture or a link to an auction and let the experts decide. "Fender Standard" is the proper designation for a Mexican made 'Standard' Stratocaster.
So "American Standard" = MIA, and "Fender Standard" = MIM.
So a serial number beginning with 'N3' will be a 1993 model and a serial number of 'Z3' will be a 2003 model. A note here for clarification, sometimes production years will carry over into the next year so it is possible to get a guitar with a serial number indicating a year other than the actual production date.
The serial numbers of both will include 5 or 6 additional digits. For example, I've got an American Standard with a serial number starting with 'N5' which is actually a 1996 model.You can ask the seller to verify which model they are selling.If you are not convinced that they even know you can compare the Ebay seller's pictures to a known model of the same year. There are some great Fender online forums out there that you can join and post questions in.Fender Highway 1 Stratocaster Upgrades ) These guitars would be rated somewhere between a genuine American Standard and a Mexican Standard model.The newest Highway 1's have the large, 70's style headstock but you have to be very careful with the older models because it can be very hard for the average person to distinguish the difference between these and the American Standard.Many sellers don't mention that they are actually selling a Highway 1.