No, no filters at all. Not even a UV. It was just after a rain storm a few months ago. Plus-X, don't remember the exposure.
It's actually a cheap-o used 28mm Tokina MM lens I was testing on a Contax 167MT to see how well the automatic aperture would work. My CZ 28mm C-Y mount is an AE version, and the MM version of the CZ lens gave me serious sticker shock. So I sprung for this lens on eBay for 20 bucks. I was pretty disappointed when I opened the box, since it looks and feels cheap and plasticy, and I thought $20 may have been too much. In fact, the construction feels so cheap I don't think it would take too much to break it.
But I gave it a whirl anyway, and it's a keeper. The glass is clearly decent.