Sentence:  The quality of these buttons and charms is best rolled gold and hard enameled in correct colors, the button having either a <WSD>screwback</WSD> or a jewelers' catchpin. 
Meaning of the word marked with <WSD> tags:  A mechanism for attaching a small item to clothing that operates by a post which goes through the cloth and a small backing plate that screws to the post. Also, the medal, tie pin, button, etc. that uses this type of attachment.