Oops.
Nice collection.
My first SLR was a Praktica MTL5 with 50mm Carl Zeiss lens just like that. Sold it about 8yrs ago, sometimes wish I hadn't but there we go.
The advantage of using manual lenses on a digital SLR is that you can see instantly if your manual settings were correct. If you were using film, you'd have to wait till the film was processed to find if there were any keepers.