As the name suggests, the game is based on Blackjack, with 4 number reels as your 'hand' and the 5th reel as the house's hand. When you push the arm down, all 5 reels spin, but reels 3, 4 & 5 have the windows blanked, so you can't see the numbers. The first two reels are your hand, and you can choose to draw 1 or 2 cards by pressing little levers under the corresponding window, then you press the lever under the 5th window to see if you've beat the house.
There is no payout on this machine, if you won, you'd tell the barkeep & he'd give you a cigar or free drink.
This machine is set up to work on 1d, but also works on modern 2p, which saves me buying 1d's of ebay!
It's not perfect, but I'm happy with how it's turned out. I still need the frame for the instruction card & the gumball door, which fits in the hole bottom left.