My 99-13 was inherited from my Grandmother. It's serial number was allotted Nov. 28, 1928-AC434350. The way my knee-bar fits up inside the case--if you look inside at the very top you will see a little latch and to the right (near the accessory box bracket) there is a little U shaped bracket- the part of the knee bar that fits into the machine goes in the U and the bar is held in place by the latch (right under the handle on the inside). Gosh, it took me about 10 times as long to write this as it will to do it! Hope yours is the same so this made sense.
You are really lucky to have the original oil can. I have everything except that. Happy sewing.
Pat