I have had my 442 for more than 20 years.
Looks like I'm not the only one that shoots high with these if ya choke way up un the grip. That spacer looks to be the ticket.
This is primarily a recoil mitigation and comfort modification, as I found that shooting the J Frame to be unpleasant at times, especially with extensive practice. I tried various types of material on the backstrap, including strips of thin rubber, before finally settling on the strip of leather that is currently on there. Then wrapping it up in Vet Wrap bandage or hockey tape. The combo I found helps soften the recoil a bit and shooting 50-75 rounds at a whack on the range is not too bad, and getting a good grip is easier.