Signet late 1960s? to mid 1970s? Signet was a brand used by Selmer on a range of instruments including guitars.  According to wikipedia the Signet line finished in 1970.

According to Vintage Guitar Price Guide the brand was assigned to acoustic flat tops made in Japan for Ampeg/Selmer from 1972 to mid 70s.

The following and image is from Craigslist “This is an American made, all Brazilian Rosewood 6 string Acoustic accept for the Spruce top. There were no Selmer Signet Guitars made after 1970. Prior to that,…all Selmer Signets were made by hand and by special order.”

So it would appear that US made Selmer Signets were made until 1970, but thereafter the brand was used on Japanese built guitars for a time.

Image eBay: