The -1 means your gun is built on the J-frame, as opposed to the 34 no dash and pre-34s which were I-frames. The I frame has a slightly shorter cylinder and frame window. The J-frame was created to accomodate the .38 special. About 1960, the I-frame was discontinued, and the I-frame models (30,31,32,33,34 & 35) were then built on the J-frame to save production costs.