The patent was filed in 1905 by Henry and Percy Seabrook, and published the year after. There is not much claims made in the patent. In fact, the only claim made is how the blade is secured.
In the words of the patent:
We are aware that it is already well known to mount a safety razor in a holder or sheath and to fix the parts in position by screwing together in different ways. We do not claim generally fixing the blade in the guard or holder by screwing but we only claim a special method of using the handle screwing through a part of the body portion for holding the guard and blade together as defined in the claims.
Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is; –
1. A safety razor comprising a body member, a suitable guard, a blade, and a handle adapted to secure said body, guard and blade together in operative relation by screwing through a part of said body member and pressing the guard and blade against the body member, substantially as described.
2. In a safety razor of the character set forth, tho use of a body-member folded upon itself and tapped by a screw-threaded opening, and of a handle adapted to screw into said opening in the folded portion of said body-member in order to secure the body member, guard and blade in operative retention, substantially as described.From British patent 1905-18684
Or in short; the blade was secured in the head by using the handle as a screw. The end of the handle pushed the blade and guard against the top cap. The drawing helps make it clear how it works.
While I don’t know how successful the Seabrook safety razor was in the market, I can see the same broad design used today. The patent is long expired, so it is free for all who wants to use it.