The Governor of Texas, Greg Abbott just signed off on House Bill 446. This bill is known as the self defense bill, which will make it legal to carry certain self-defense items on your person starting on September 1, 2019.
Once the law goes into effect, brass knuckles, clubs and kitty keychains will be legal to have. The law does specify though if anyone that committed or commits a criminal offense using one of these weapons prior to the law change will be held accountable for committing a crime. The offense will be punishable by law up to one year in jail and or up to $4,000 in fines.
Currently, the Texas Penal code, section 46.05 classifies brass knuckles as a prohibitive weapon. Having one in your possession, even repairing or selling them is a class A misdemeanor.