Formal:
* Precedent: This is a legal term for a previous case that is used as a model for future cases.
* Benchmark: This refers to a standard or point of reference against which something can be measured or compared.
* Model: This can be used to describe something that serves as an ideal or example to be imitated.
Informal:
* Prototype: This is an early version of a product or system that is used as a guide for later versions.
* Template: This is a pattern or design that can be used as a guide for creating something else.
* Blueprint: This is a detailed plan or design that can be followed to create something.
* Guidepost: This is a landmark or sign that indicates direction or provides guidance.
* Touchstone: This is something that can be used as a test or standard for judging quality or authenticity.
The best word for you will depend on the context.