Tony,
The original marks are the B.A.XIX.16 and the size stamp. The rest are re-issue stamps. "B.J.A.Chemnitz18" stands for Bekleidungs-Instandsetzungs-Amt Chemnitz 1918. This was the repair section of the clothing office in Chemnitz. Once repaired, the cap was given a new Garniture classification. The "g" and the "gb" indicate it was suitable for garrison wear, but in worse condition than normal. These stamps are in black, which indicates that they were made after January of 1917, when the color of the stamps were changed from green. Unfortunately, I cannot decipher the smudged regimental stamp.
Chip