I was digging through my stash of stuff and came across something I didn't remember I had. I figured it was worth a cleanup with fine steel wool and apply some gun oil.   

It's marked IDEAL MFG co. New Haven  25-20 M. 

The brass sprue plat screw looks to be a replacement.  The bullet mold looks good and I'd guess it'd throw a bullet of about 100 grains. I suspect it's still usable.

I would guess that bullet is closer to 86 grains, but hard to tell from looking at the picture, just going by what the couple I have owned did.

John Barlow's patents of 1884 were the basis of the Ideal series of tools, the small caliber tool with the bullet sizer was the #4 tool, larger caliber/length tools of this type were #6 tools.  If marked 25-20, would be 25-20 singleshot, later mark added ss.  When the WCF cartridge was added they were marked WCF or 25-20R for repeater.  About 1910 Barlow died? and Marlin owned Ideal for about 10 years and marked the tools with their name.  Afterwards the Ideal company was reorganized under that name until absorbed by Lyman.  Ideal tools were numbered 1-10 with the possible exception of #9.  Lyman combined #3 and #10 to become the 310 tool.  Suggest Chamberlin and Quigley - Cartridge Reloading Tools of the Past.