Number of games played on a pinball machine

When buying a pinball machine, condition is everything. Condition is dependent of a lot of influences, like how the game was stored (humid environment, indirect sunshine, ..) but one of the major influences is the the number of games played. You can compare it to the amount of miles on a car.
Games with many plays will have wear. The mechanical parts will have worn and have more variance, this will result in coils with less power or a more sloppy feel. The playfield and other metal parts will be worn of pinballs passing ten or hundredthousand times.
Games that have been stored in identical conditions, will look and feel different because of the number of games played and how worn everything is.

Luckily, pinball machines are commercial machines and designed to be played. They don't break down or wear after a few dozen games. In the past when games spent most of their lifetime on location, they'd get tens thousands of plays. Some over a hundred thousand, if they earned well. And if they were regulary cleaned and maintained well, they'd still look and feel to be in great condition.

It's only the last decade that many games are also being bought for home use. A lot of the pinball machines produced will never see those kinds of gameplay numbers. Even after 10 years they're practically still brand new.
Sometimes you see games for sale that have a really low number of games (sometimes even only 50 or a few 100). People that focus on very low number games, are usually not players but collectors that want to look at shiny machines.

Please don't make a decision to buy or not buy a game only on the number of gameplays. Just use it to see if a claim of being home use only is valid, and to have an indication about its maintance and its price.
A game with less than 200 games is practically brand new, you won't see much difference with that or one that's just taken out of the box.
Machines with less than 3000 games played are probably home use only. It depends on how old the machines is, if the owner had other games, ..
If you encounter games that aren't too old and have over 10.000 games played, then they've probably been on location. Only on these games I'd take a good look at the mechanisms (motors, servos, ..) and maybe consider that you'll have a cost to replace some parts. On those games you'd take a good look for wear that indicates location play : wear on the coin slot, near the flipper buttons, ..

So how can you know exactly how many games were played on a pinball machine ? On a lot of machines, you can never know exactly.

Electro-mechanical pinball machines

Many electro-mechanical pinball machines have a mechanical counter. Usually it's located in the bottom cabinet, near the coindoor. It keeps track of the number of games played. Especially machines made in the 1970ies have them. Older games usually don't have this installed, or it was not installed from the factory.

Game counter on Bally Fireball

You can just read the number of games played. Is it correct ? Who knows. Usually it is. On machines where it was not installed by default, you never know when a operator installed it. Was the game brand new or did the counter get installed later during the machines life ? And with factory installed counters it's always possible a wire was disconnected for a period and the machine didn't count all plays. So while it's not an irrefutable number, on most machines it will give a correct number.

Electronic games

Almost all electronic games, from 1977 until around 2010, require some kind of battery (chargeable, AA, ..) to keep data in memory. If the battery is empty or gets disconnected, all settings and audits (like earnings and games played) will be lost forever. Upgrading a machine, installing a new rom version, almost always also clears all settings and audits. So for the majority of electronic games, it's impossible to know how many games were played exactly.

Game counter on Zaccaria Pinball Champ 82

Some electronic games may have a mechanical counter installed, but is exceptional. That would be something that an operator did himself, and was not installed at the factory.
When buying games from an operator sometimes the audits were not reset in many years and the original batteries are still present. Such games have their whole adit history (I remember buying some WPC95 games from an operator that probably never had its audits reset), but once the audits are erased, they're gone forever.

On most electronic games you should assume that the total number of games displayed is not the number over the full lifetime, but has been reset when batteries were replaced or when the software was upgraded. There is no way to have absolute proof that the number displayed is correct.

Even on very recent games like Jersey Jack Pinball machines, the number of games is not known with certainty. Some software upgrades are incremental and preserve the numbers. Full install upgrades will wipe everything. There is a procedure to save settings and audits before doing an upgrade of the software. If a user installs new software following this procedure, the original audits will be imported. However if a user doesn't save their settings and does a full install, the number of games played will start at 0 again.

Game counter on Attack From MarsOn WPC and WPC-95 pinball machines audit B1 - 06 indicates the number of games played (since last reset).

Stern pinball machines

Stern games made in the last decade do have a 'lifetime' audit settings which is not erased on software upgrades or when the battery dies. Forcing it to 0 involves replacing almost all expensive boards in the game. So these are the only type of pinball machines that are designed to keep track to give a correct number.

Game counter on Stern MetallicaMetallica only has an older style of number of games, that can be reset.

Game counter on Stern MetallicaMetallica does have a lifetime audit of total paid credits.

From whan I can find the lifetime audit was implemented around 2012 with the AC/DC pinball machine. These first generation of games does not keep count of the total number of games, only of the earnings. This is useful for an operator (it prevents tampering with the earnings by the location).
For games in a home use setting, it's still useless in knowing the number of games. Most home owners don't install a coin validator and keep their game on free play. For their games the lifetime earnings will remain 0, without giving an indication of how many games have been played.

The lifetime earnings audit is useful to decide if a game is really Home Use Only (HUO).
It often happens (on purpose or accidentally because people don't know exactly what HUO means) that games that were used on location in their first years, still get sold later as HUO, or as 'HUO the last X years'. People forget what 'only' means :)
A true home only game will not have a coin mechanism installed and will have lifetime earnings audits 0. If there's a substantial number, the game probably was used in location for some part of its lifetime.

The number of lifetime audits has been expanded later (possibly with the Spike boardset). More recent games also display a lifetime total plays count. It will keep track of every game started, also on free play in a home environment. That lifetime count is the only reliable number which is difficult to reset. So when inspecting a game for sale, look at the lifetime audit number.
But as I said in the beginning, this number doesn't say everything.

Game counter on Stern Iron MaidenIron Maiden does have a lifetime audit of total games played.