Current version of Mir-1 lens is known as "Mir-1V" (or "Mir-1B" in deference to the original cyrillic marking).
The optical formula on either lens appears to be the same as the original Mir-1. There may be some coating quality differences, and of course, the most obvious difference is the lens mount.

The lens is still made today by KMZ in Russia. When buying this lens, make sure it says "MIR-1B" or MIR-1V" if you're planning to use it in an M42 camera. Many Mir-1 are the older Zenit M-39 mount and will not fit to M42 mount without proper adapter.

The lens requires a good hood when shooting into the sun. The 37mm focal length may seem a bit odd, but its field is comparable to a 35mm lens. In fact many 35mm lenses have real focal lengths which are longer than marked. The Mir-1V just happens to be candid and honest about it.