Elbo,
Welcome to the QB.
According to ISMACS here: {
http://www.ismacs.net/singer_sewing_...-database.html }
what you have is a Singer 99K, 1 0f 50,000 allotted 9-13-55.
The K indicates it was made in Clydebank, Scottland.
The 99 K is a 3/4 size machine.
Manuals can be had at ISMACs as well as much other information.
{
http://www.ismacs.net/index.html }
~or~
Singer: {
http://www.singerco.com/accessories/instruction-manuals }
As far as being "worthy", it's a very capable machine. Of course this all depends on the mechanical and electrical components being in good shape. Most of that is an easy fix if needed.
Joe