I don’t know what they are but I have a feeling that when aucoonhunter reads this that he’s gonna know what they are

Those look like piss poor markers for a long time growth study. Usually I've seen aluminum tags instead of something like those.

It’s in about 10 acres of rather big pines. On timber company land. The 10 acres is surround by river on one side and swamp on the other three. Pretty much no way to get too it without going through acres of swamp. I will get some more pics of em next time I am there. Some are in four or dive foot squares. The stakes are one inch aluminum about 16 inches long.

Test plots for timber company. Years ago timber companies planted trees an marked every tree in a plot. Sometimes lot different plots with different types of trees an fertilizer . The numbers are probably date of planting,type of tree an what kind of chemicals was used or site prep. They would survey them every so often to check growth of trees in different area an soil types. Most companies don t do it any more because they sold land to a different company but the test plots are still there if they haven t been logged yet. From size of tree them probably 25/30 yrs old. I ve seen loblolly pine, short leaf, aspen, many different oak an poplar in plots on land that international paper owned (formally champion).

Treasure, I melt down all that aluminium.