The most common farm toy scale, 1/16, covers thousands of toys, making this list highly subjective.
1. John Deere 430 tractor (the green model in the photo above) with or without a 3-point hitch. These models, made in 1958, could sell for as much as $2,000 NIB.
2. John Deere 630 tractor. The 1959 version by Ertl Co., Dyersville, Iowa, offered with or without a muffler hole, is the rarest.
3. Allis-Chalmers WC tractor. The father of farm toy collecting, Fred Ertl Sr., made this as one of his first three farm toys. "I've never been able to find one," says Rick Campbell, a longtime collector from Apple River, Ill.
4. Farmall H. This narrow-front tractor, often called the "Ertl H," is the second of the earliest Ertl tractors. "Like the WC," Rick says, "the Farmall H is super-tough to get."
5. John Deere A (the silver model in the photo above). This early Ertl model variation (the third of the three early Ertl tractors) comes with aluminum wheels and is difficult to find. Rick says he had one of these with rubber wheels, but never the one with metal wheels.
6. International 1026 tractor with "Hydro" on hood, made by the Ertl Co. in 1970. Kate Bossen of Bossen Implement, Lamont, Iowa, says it's tough to find a good original of this farm toy that hasn't been repainted.
7. Cockshutt 1850. This model was made by the Ertl Co. in 1968, and is a narrow-front version in tan and red. It came with or without fenders. "That's one you don't see around a lot," Kate says.
8. International Harvester 966 tractor with white front wheels. "That's been kind of a hard one to find," Kate says.
9. Agco-Allis 9695 tractor, unknown to many collectors. "Each dealer got one if they attended a certain meeting," Rick says. "After that it was never decaled for a shelf model or collector model. It's rarely seen at a toy show."
10. White 6215 tractor. Rick says a short run of these tractors was made in 1994 with a straight frame. "Later models had cutouts or valleys in the hoods so you could turn the wheels sharper," he adds.