Component side on large metal component closest to insertion end
Ts 648 b
On bottom - upper left side
overall: 1 3/4 in x 3 3/4 in x 7 3/8 in
This Z23 circuit board has heat marks where some components are attached. There are two inspection marks on the component side. The handwritten description on the sticker reads "getestet 17 20A stromuers. (2N512) OV. 9.9.71".