In terms of dollars, not a whole lot, but in terms of build quality/durability, looks, performance, and coolness factor for the owner, probably a lot more.

I'm pretty sure your machine has only one wash arm, so you'll have to be more careful about how you load the bottom rack in order to allow the spray to reach the items on the top rack. 

The experts among us here will have more detailed advice, but if it's a low mileage machine and you're willing to take the care to load it properly, it should perform well for you.

Sounds like a portable KDS16 to me, that is what a KDS56 was I do believe. And yes, it's a one-arm wonder.   This is like from the late 1960s to the early 1970s.  It will clean very well is care is taken in properly loading it as Ralph indicated.  Just depends upon what all you put in your dishwasher and how intensely loaded it is. 

This is my all-time favorite classic KD DW. I have had this model in my service kitchen in the W Va, house for over 20 years and it does a great job if loaded properly. The only real drawbacks are that it uses three times the water of your new TT KM DW and it requires a hot water inlet temperature approaching 140 degrees. As we are are on a well and the machine is lightly used I didn't worry about the water consumption so much. And since we are all electric and I don't like keeping my hot water above 130 I rewired the  sump heaters so both would be used when ever the machine was boosting water temperatures. Rewiring them this requires you the have the DW on a 20 AMP breaker with 12Ga wire, but boy does it clean and does so in a little over a half an hour.

So the only real negatives for me are having to load it correctly because of the single wash arm design and having to clean a messy stinky filter every once in a while. If I were you I would use it, think of having a brand new 1968 car to drive without most of the negative parts.