Diamond in the rough

[John Stickney]

I recently brought this beauty home, much to my wifes' dismay, and am still researching before I begin restoration. So first things first. Hull#23608. Number on edge of armour is CT267144. Painted on the let side is #S3.913. I'm trying to find out what this means. On the right rear of the armour is what appears to be a red shield with a rook on it. Perhaps a regiment or unit insignia? I'll post pics when I figure out how.