Yes it is just a machine that has not been out on route. Which means it probably has much lower plays on it than a routed pin.

In most/all cases someone keeping it in the home all it's life will not see as many difficulties as a routed machine. I suspect my machine was HUO, but there was no way to confirm so that wasn't claimed.

I know I don't have enough friends to give any machine, even MM enough action to equal as much as an arcade/pizza joint.

Mine has no lock on the coin door area, just a knob so I can easily get into it, but I don't think that's a commonplace thing.

Yes, HUO machines tend to be in a lot better condition than machines that have been routed out in arcades, bars and fast food joints. There's no lingering smell of beer or tobacco inside the cabinet (unless the last owner smoked whilst playing at home) , and have less dents or scratches in the cabinet/backbox too.

As has been said, normally a HUO machine has been played a lot less than one out on a route, and has been cleaned and looked after a lot better, so the playfield is usually in a lot better condition.

Am I correct in saying that some of the more recent Sterns delivered NIB to collectors have turned up without any coin mechanism fitted to the front door?

You have to be careful and ask - is it HUO or very nice looking restoration ?
so many talented ppl in the hobby do such excellent work

HUO is over used as a term to describe condition.

You can have a pin in a smokers house that has no idea what they are doing. May never take off the glass to clean he playfield. Could have broken plastics, blown out scoops, etc.

I think the biggest thing about HUO pins, is that they aren't turned ON in attract/GI meltdown mode for 12+ hours a day, every day, in some place with temperature fluctuations, rough players, etc. HUO would have tons less strain on the machine itself.

It is the difference between buying a used car from the original owner verse buying a used cad from a cab company.

I agree, like routed then put into a home and that makes it's current status HUO.

Anyone doing this is trying to pull a fast one. 99% of true HUO pins you can tell right away just by looking at the shooter lane. I've had some people try n sell me games n trying to pass them off as HUO and if you've been around this hobby long enough you can tell right away if it is or not.

HUO could also mean more when picking up newer sterns since the clear is not as thick as past pins. My AFM I bought from an op and it had a credit meter inside the coin door and it had over 24k games on it and it looks fantastic since after about 2 months he installed the upgraded scoop and cleaned the playfield n changed the balls every 3 months. The playfield shines better then the IM I unboxed in may of this year.

Don't be afraid to buy older pins cause they aren't HUO just be sure to inspect the major wear areas.