The image on the left is a very coarse representation of the relief seen on the rusty lump of iron shown on the right. The iron is presumed to be the door of a wood-burning stove, excavated recently on a plantation in East Texas and probably around 150 years old. (This door is now on display with other artefacts found in the vicinity. It is part of a growing collection of fascinating items in a small museum. See the West River Plantation website: thewestriverplantation.homestead.com)
Unfortunately, the oxidation has destroyed any fine detail there might have been on the cross piece, so we only have the general shape. But it is clearly not supposed to have been anything functional - it's neither a door handle nor a brace to give the door strength.
You'll notice that the cross arms are short and stubby compared to most crosses, supporting the notion that the artist wanted to give focus to the cross arm ends. The door's owner wondered whether the blobs in the centre and at the arm ends represented acorns, domes, helmets or bells, each of which have their own symbolic meaning. He also wondered whether the design was a stove maker's trademark.
However, the intended meaning for the symbol is now understood. As with many such mysteries a hint can be found from the context, and in the case of a stove, the context is heat. The points of this cross represent the flames of candles in prayer for humanity in the four corners of the world. This cross signifies the evangelization of the world. The middle beam represents the Father with the side bars the Son and the Holy Spirit respectively, and the circle in the centre is a symbol of eternity.
Alex Roman tells us that this cross is popular in the East, particularly in Georgia.
See other crosses with flames.
Puzzling symbols index