That is definitely a swm lnb, its a very old one, one of the originals before they went to green labels. Should work fine though, but you will need a power inserter, I don't know of anywhere you could pick one up locally.... may check craigslist.
They are around $10 on amazon. You need the 21 volt model.
Amazon product ASIN B001YHBYXA
If the setup was working before I would follow the entire length of the cable just to make sure one isn't installed already but unplugged.
You can use a 29 volt model with a swm lnb, too.