Okey I had this lens before. I came from the country and city which produces this lens. PHENIX is originally a Shanghai optical company, and during 1960s and 1970s it moved to the inner land.
This threat is kind old but I just hope who asked this could have some general idea about "Chinese lenses". I used to keep Pentax M50/1.7, Ricoh 50/1.7 and PHENIX 50/1.7.
As you all know that there are not a lot of BIG NAMES in China like NIKKON and Canon. However this does not mean that China cannot make lenses and cameras. And 50mm f1.7 is not a something very difficult, so.
I think the price for this lens, when I got that it was 280 RMB (around 40 bucks).
For the in-depth review, here is a link:
http://www.cnpentax.com/thread-209-1-1.html
Personally I like this lens (okey, "emotionally"....). It is metal, nice quality.full-open useable (still soft), though some CA exists; and according to that post, it even performances better than the M50 @F2.8.
It compared the PENTAX/RICOH/PHENIX. I know it is in Chinese but plz try google translation.
Besides, FYI SEAGULL is another Chinese optic company. on Amazon it sells zoom viewfinder. Yongnuo, another brand is making not-bad flash.
Hope these can help you.
Best,
Bing