This was Colt’s first double action revolver, and was made from 1878 until 1905. In .38 caliber it was called the “Lightning,” and in .41 caliber it was the “Thunderer.” These are the standard grips used by Colt for most of the Lightning production.
Dimensions / Sizes
Measuring right panel from backside:
1 5/16″ along straight line @ top
29/32″ along other straight line
2 15/26″ long when standing grip on its top & measuring vertically (not diagonally)