Somebody correct me if I'm wrong, but it's my understanding that all MB breechblocks were machined out of low carbon steel (pretty much all that was available at the time) and carburized (case hardened).

According to John Dutcher's book, the breech blocks on all Ballard rifles are the same material. Only difference is the 4 variations in design. The DST block, single trigger CF, single trigger reversible firing pin, and single trigger .22 RF #3 style. I have heard of a DST block with reversible firing pin, but not seen one. I've owned three #2's with DST, and all were CF only. Assume they just grabbed a CF DST block for those special order #2's. One was .38 Long, and other two were .32 Long.
PS-The #3 .22 rimfire block is the only breech block without a firing pin retaining screw. Have to split the blocks to replace a firing pin, which always puzzled me.

Crown-C wrote on Nov 23^rd, 2021 at 4:01pm:


Good to know there's more out there! With that serial number it must be a "Marlin Firearms Co." marked receiver too.

bobw wrote on Nov 23^rd, 2021 at 7:28pm:


That's an odd breech block Bob. It appears to have a full length DST plate, instead of the usual short plate that stops shy of covering the entire bottom of the breech block halves. It also has one rectangular opening for the dual firing pin system, instead of the twin holes I usually see.
I wonder if this is a very early breech block, as those I own with very low numbers have the full trigger plate. But haven't seen the rectangle hole before, and wonder if it was possibly modified?
The firing pin screw location is correct for a reversible firing pin breech block also.

bobw wrote on Nov 23^rd, 2021 at 7:47pm:


The serial number is on the top tail of the two block halves. On each half, and should match each side. If it's not there, then somebody has removed it for some reason.

Bobw,
The serial number should be all the way to the rear of the block tail. It curves there and your photo may not catch it, especially if it’s a low serial number block. Might check that first when you get the chance to look at it. I’ve never found any serial numbers inside the two halves of the block. I have seen a few that have had the sn removed I presume from polishing.

Yes, you'll need to look at the tail of the blocks from the rear angle to see the serial number. Since your block appears to be of the very early variation, I suppose it's possible it may have been ordered as a replacement breech block, and might not have a serial number.
These early style breech blocks fit somewhat odd, as the whole trigger plate sits below the bottom of the receiver, and appears to be a poor fit compared to later flush fitting  receivers. I have two Ballard rifles with this style trigger plate, and it appears Marlin added the trigger plate to the breech blocks without milling the blocks to recess them. So the completed DST blocks sit the thickness of the plate below the action. And unlike later DST blocks the trigger plates are full length of the breech block bottoms.
You can see the way they sit on my Pope takedown Ballard action here:

(You need to Login or Register to view media files and links)