The model number is stamped between the top two screws of the stitch length lever. It is a 185 but I think it's a K not A J. We have one that looks exactly like it and ours is a K.
In reality it's a Singer 99 in a different body.
To thread it:
Take the thread off the spool, to the left then around the little hook shaped thread guide.
Down to the top tension ( make sure the presser foot lever is up ) then around the bottom from right to left.
Then up and over the spring and back down to the left then under the shiny hook.
From the hook up to the thread take up lever
Through the hole in the take up lever from right to left
Through the two guides on the face plate, down to the needle
Through the needle from
left to
right.
Hope that makes sense.
Here's ours:
I've cleaned and lubed it and put a new spool peg on it since this picture was taken.
Joe