I used to get free metal detecting magazines back in the 60's and 70's.
But I can't hardly remember their names. Whichever ones were distributed
by Peterson Publishing Co., and the Curtis Publishing Co., we got free.
My dad used to work for Curtis Publishing back then. We would get
"returns" which were magazines that were returned and credited
that didn't sell off the racks when the next months issue came out.
We got to keep all we wanted as long as he ripped the front cover
off and returned the cover. So I got zillions of free magazines when
I was growing up. Many good ones like Rod and Custom, Hot Rod, etc..
All different kinds, including many comics.
And the metal detecting rags were some of them.. Heck, I've might
have read something of yours in one when I was a young pup..

Course, I didn't have any money then, and couldn't afford the machines
I used to drool over in the mags. They had lots of treasure stories. I
remember that. If that mag says Peterson or Curtis on it anywhere,
I once had a copy of it most likely. But I don't know if they distributed
Western Treasures or not.