Hi Tom! Welcome to the forum.
Your lens is the SMC Pentax
A 50mm f/2. All "A" series Pentax lenses are manual focus. You have a Tiffen filter attached to the front, I'd unscrew the filter for use on your digital camera, but you can try it out with it on and off and see what you like. This lens was a standard lens that came with cameras bought during the time it was produced.
The A on the aperture ring means automatic aperture. This means the camera can control the aperture in Av mode. Older M and K series lenses require you to turn the aperture ring to set the f-stop, but not with A lenses as long as the "A" is selected on the ring.
This lens isn't too bad, but I wouldn't ever consider it a sought-after lens. There are better primes and people may give recommendations here, but without knowing your budget I'd suggest you take a look at the lens database here and see if something catches your eye. The database has reviews and specs for each lens in the K, M, A, F (first auto-focus lens series), FA and DA series. Specs include whether it's autofocus or auto aperture, etc. Here's the link to your A 50 review:
SMC Pentax-A 50mm F2 Reviews - A Prime Lenses - Pentax Lens Reviews & Lens Database.
Again, depending on your budget, I'd recommend the FA 43mm f1.9 Limited lens. It's one of the finest lenses available and my personal favorite. It works well with a K-5 and a K1000.
Edit: I was typing my reply while Boris replied. I also think the DA 35mm f2.4 is a good, inexpensive option. However, be aware it won't work on your K1000.