When I searched for "When had you met him" in Google Books, I found "Warren Commission: Complete Investigation & Commission's Report", which includes:
Mr. GRIFFIN. Do you recall how long Jack stayed in Havana?
Mrs. NICHOLS. Not exactly; but I would say he was there from a week to 10 days.
Mr. GRIFFIN. Did he tell you why he went to Havana?
Mrs. NICHOLS. I thought it was a pleasure trip.
Mr. GRIFFIN. Did you see him off at the airport?
Mrs. NICHOLS. No.
Mr. GRIFFIN. Did he tell you who he was going to visit in Havana?
Mrs. NICHOLS. The only person he told me he was going to see in Havana was a man by the name of McWillie. I don't know if Mr. Mac was his first name or whether McWillie was his last name.
Mr. GRIFFIN. Had you ever met McWillie?
Mrs. NICHOLS. I had.
Mr. GRIFFIN. When had you met him?
Mrs. NICHOLS. I had seen him a few times. Jack had introduced me to him. I had seen him in the Vegas Club a few times.
This looks like a testimony of a witness (Mrs. Nichols) related to the assassination of President Kennedy.
Why did Mr. Griffin ask Had you ever met McWillie? instead of Did you ever meet McWillie? or Have you ever met McWillie?? Similarly, why did he ask When had you met him? instead of When did you meet him??
Could the last four lines have been something like this instead?
Mr. GRIFFIN. Did you ever meet McWillie?
Mrs. NICHOLS. I did.
Mr. GRIFFIN. When did you meet him?
Mrs. NICHOLS. I saw him a few times. Jack had introduced me to him. I saw him in the Vegas Club a few times.