If The Service Is Due....Charge it.......Else Keep It....
It Will Be A Pure Refrigerant But If They Fill It Will DESI Techniques And Tools......I See No Difference On How Good Gas You Charge...It Will Mess Up...!
So Use It Till Its Working zFine And When Needed....Refill This One After proper Vacuum....Leak Check...Compressor Oil Top-up And New Filter