Seeing as how the Horse,s head is only in silhouette,...and by the looks of it, 3/4in ply,..there is every indication, that this,is,nt an expensive Rocking horse,but having said that,...just because it does,nt have a full body,does,nt mean to say, it did,nt cost a bit when first made...This may be one of these.... or similar...having looked at this horse more closely.i can see that its is all silhouette,with just a flat seat,which now screams at me..."flat pack"...my only hope is,that your Grandfather, did,nt pay way over the top,.but having said that, even as a flat pack,from the company below, you,d be paying £200/300.+..but this one of yours,is,nt one of these,....therefore there is every indication..that this is a cheaper version....or possibly, shed built..
http://www.rockinghorse.co.uk/rocking-horse-timber-packs/swinger-rocking-horse_3a_-timber-pack-_5f_-flat-head/