Enter the “Magic Window”. It is defined by Veteran’s Affairs as the year after leaving service for your country. You have to have records of a condition worsening after you left.
My dad worked at the Rocky mountain arsenal when he was 18 years old. I believe they were neutralizing sarin gas and mustard gas. They didn’t wear much in the way of hazardous materials protective gear way back then.
I’m curious about potential exposures at a Maryland Army base in the 1950s, Is this too long ago to look into? Is it pointless? My father wound up with prostate cancer, but many decades later. He ultimately died of a brain tumor at age 80.