Started with a Garrett. I think I've probably tried everything make and model from 1977, all the way to the up to the E-trac and GPX 4800.
Nothing new as for me now, I am pretty much handicapped.
JTW. In your bottom picture, does that pattern look familiar? Looks exactly like the border of that rug/table runner you had from your other post about the cloth.
Until someone pipes in - I searched Google and found that Matt, etc. are correct (but they knew that already!)
Sri Yantra - The Sri Yantra is the visual expression of the sound of om. This pattern is seen by monks chanting the om. It has also been recorded electronically as a pattern which emerges...
Not sure of size, etc., but that last picture makes it look like a chimney cover. Flue cover.(the kind you put over the hole in your house that had a wood stove.)