Upholstery advice needed!

[FenellaFerranti]

I'm attempting to reupholster a chair and am a bit confused. The back of the chair has hessian webbing and 6 springs on it but the seat of the chair just has some very poor looking stretchy plastic webbing and a foam pad on top. Everything I've seen seems to say seats are sprung more often than backs. The chair is pretty old and from the holes in the woodwork I'd guess has been reupholstered at least once - do you think originally both seat and back would have been sprung? Or are some chairs just that way round?

Sorry if I'm not clear, still getting my head around all the terminology! Thanks!