I bought my first Workmate (the classic cast aluminum frame type) at a garage sale at least 15 years ago. It was in relatively good shape with a plywood top. About a year ago I bought another used Workmate of a similar vintage that had one small difference… the top was particleboard instead of plywood. I tend to leave the Workmates outside year-round for projects and found that the particleboard did not, to put it kindly, hold up. After a year of Oregon rain, notice how severely the top is delaminating/disintegrating.
My other Workmate, left outside for 15 years, is very slightly warped but completely serviceable:
As you can see, the top is scarred from use but in great shape, even wet:
My small bit of advice in buying a used Workmate: unless you intend to only use it indoors or put it away promptly after use, get the one with the plywood top! I’ll have to make a new top for the disintegrated one now, won’t I?