Wow! I haven't seen one of those since the '70's, except of course for decoration!
I looked up Siren 17, nice
trailer boat with a cuddy
cabin. Not sure where you'd mount one of those, but modern usage is to have throwable seat
cushions on a boat (required in US by USCG) in addition to one life jacket per person aboard.
If you really want to
repair the life ring get a
canvas shop to replace the 4 straps & the line going around the ring, might cost more than a new one. Or just pull out the old line & thread in a new line with a splice or
knot to finish it.
This type of ring is normally used with about 50 ft. of line to enable pulling the ManOverBoard back to the boat.
Hope this helps & the Siren sure is a cutie!
Capt Wayne