This is a genuine vintage Seiko clasp extension crafted to provide .25” to .5” of length to that bracelet that’s almost there. It is only designed to work in tandem with the type of clasp pictured that was widely utilized from the mid 1960’s through the 1980’s. The top surface is a matte sand blast, and the corner bevels are polished.

(*Note- This is the only one i’ve ever seen, and do not have a source to procure any more. It does not come with the bracelet pictured.)