Stanley Bailey planes don't have Stanley cast into the base. Stanley should appear on the lateral lever, the cutting iron and possibly on the lever cap(although yours does not have one of those).
One patent date behind the frog makes it a type 13(1925-1928) or type 14(1929-1930). Probably not rare, Bailey No.4 planes show up a lot, everywhere, especially on eBay.
If all it needs is a lever cap, you can find lot's of those on eBay as well. I have a small box full out in my shop.