I did a little digging on the Marlin Sighting-In Guide.
First offered in 1956,,or '59 depending on who you read,,,a circular carboard design.
Updated in 1963 to a rectangular design and made of white plastic .
After that the rectangular style stayed,but the graphics changed a bit as did the material they were made of..
The 3rd style was made w/a cardboard insert and a plastic sleeve.
4th style w/both parts of cardboard.
A 5th style was made with both parts of cardboard but had the corners reinforced with small rivits for strength.
They were sold by Marlin by mail for usually $1 or less. Often give-a-ways at public presentations and shows.
Sometimes included in with rifles sold w/a Marlin marked 'scope sight.
(Scopes weren't mounted, just included. That avoided increasing the value of the firearm for excise tax purposes. Don't know if they continued that practice later on)
5th style Sight-In Guide was last printed in the mid 70's. and ran 'out of stock' from their parts & service dept around 1980.
Your's looks like an all cardboard material made one,,so a 4th style I guess from the info. Unfortunetly I couldn't find any dates when they were released other than the 1963 date when the switch to the rectangular format was made.
A good guess would be late 60's. I recall them being around the place when I worked there in the early 70's. I remember them being cardboard construction,,at least part or it,,maybe all. Other than that I didn't pay much attention to them.
You know how that goes,,,
Nice little momento to hang on to from the family.
