You have a very nice HA-1 / 15 clone. One of about 16 gazillion made. I have 4 or 5 of them and no two are the same. My first one is made by JUKI. The others ?????
TRI-FLOW, TRI-FLOW, TRI-FLOW, never mind the regular sewing machine oil. Tri-Flow has special solvents in it to loosen and dissolve the oil gummed up oils and it's got PTFE in it which does a really slick job of lubricating.
Oil all the holes on the top of the arm, pull the face plate and oil every thing that moves in there, and tilt the machine back and oil everything that moves under there too. You'll see lots of tiny little holes on the articulating parts under the face plate and on many parts under the bed. These are oil holes.
Check the motor. Where the main shaft is on each end there might be an oil hole there too. Give it a couple good drops of oil if there are holes, but don't flood it.
If you see a J- A with a number under the bed somewhere you generally can tell who made it. Not all of them have one though.
Joe