How to now if a Combined vcf file is calibrated with GATK or not

Dear GATK using community
Pardon me for my ignorance, but I am new with using NGS pipelines. I have recieved a combined VCF file or 200 samples. The only information I was able to understand from VCF after opening it in command line and usegalaxy online server the variants are called by using Haplotypecaller of GATK tool. How can I identify that if the variants are only called using haplotypecaller or they were also validated or calibrated afterwards.