I stopped doing this but since I see there are three bids on this item, I thought I'd come on here and inform in the case that one of the bidders might be a user of this forum.
Despite what the ad says, this is not a 1951 Henry J mirror:
https://www.ebay.com/itm/Henry-J-1951-rear-veiw-mirror/183790266121?hash=item2acac0e709:g:u94AAOSw7q5cxJoOIt might fit a '53 where the stem mounts to the windshield center bar but it is not a Henry J mirror of any year or model.
The '51-'52 Henry J mirror is rectangular and has a long offset stem which mounts through the headliner:
The later mirror used on the '53s is this one:
The one in the ebay ad may sub for the later one but you'd need to have chrome trim that has a mounting hole on the center bar if you intend to use it in a '51.