Hi Robert,
Two are the last model 18 , they are without the edger slot on the top of the base.
Two others are the first model 18 , they have the two threaded holes on both sides on the base.
If you google Vintage mowers you will find a site then look at the Victa section and it shows the differences.
They are not worth $400 in my opinion as only one has a recoil starter,not original colour , should be hammer tone paint and missing edger covers and original air filters.
You can buy these mowers that need painting for $50 to $150 , check eBay to see prices.
Cheers
Max.
