Iver Johnson id help

[Templar32nd]

I'm needing help dating this.38 s&w, top break, hammerless. The appearance of the letter J prefix to the serial number is odd to me. It's also only found in One location on the firearm. Not both.
ImI hoping to be able to post pictures as well. Thanks, in advance. And thank you guys for letting me join this forum.

 

[theotherwaldo]

Here's some basic info from Guns.com.
Here's a book by William Goforth on Iver Johnson guns that I've been considering: https://www.gunshowbooks.com/cgi-bin/webc.exe/st_prod.html?p_prodid=GS37205
I've got one that's much like yours that's been in the family for about a century.

 

[Curator]

2nd Model "Safety hammerless" revolver made for Black Powder sometime between 1995 and 1907.