Both your engines are 2 hp Briggs and Strattons, Model 60102. That is the normal post-Kirby-Lauson engine for the narrower SB45s, and was quite a nice engine at the time. The time was 9 June 1969 for the first one and 14 May 1969 for the second one - a very closely matched pair. The blades of the reel you have shown look a bit wavy, so it has probably had some bad luck in its life, but not necessarily anything serious. The blades have plenty of meat left on them and have probably never been sharpened. The sprockets do not look seriously worn. The chains are under-lubricated and probably a bit rusty, so they will need some basic cleaning and lubricating, during which you can easily check them for wear. I can't see the engine mounting deck in the pictures of the assembled mower. The disassembled mower has a one piece deck, which is consistent with it being an early SB45.
I'll leave the more technical comments to Deejay, who is a serious SB guy.
