# APF MARK 55

The APF MARK 55 is a scientific calculator with 12 digits precision and RPN (reverse polish notation) logic. It has 45 functions, 30 keys, and an LED (light-emitting diode) display typical of calculators of this era. The power source is 3xAA sealed.
**Note:** Similar to HP calculators.

## Facts at a glance:

Feature | Value |
---|---|

Type | Scientific |

Functions | 45 |

Keys | 30 |

Precision | 12 |

Logic | RPN |

Display type | LED |

Length | 159mm |

Width | 76mm |

Power Source | 3xAA sealed |

Year introduced | 1977 |

## Replacements:

If you have an APF MARK 55 that is no longer working, you can first try replacing the 3xAA sealed batteries. If that doesn't solve the problem, then you can consider replacing the calculator with a modern equivalent.

We suggest the following current model as a replacement: