# What are Model-Based Stamps: Ethereum and NFT

## What are Model-Based Stamps?

The Ethereum and NFT Stamps are backed by supervised machine learning algorithms that score your address based on your wallet's transaction history. The Ethereum Stamp examines your activity across Ethereum Mainnet (L1), Arbitrum, Base, Optimism, Polygon, and zkSync, while the NFT Stamp only looks at activity on Ethereum Mainnet (L1). 

The higher score you get, the more your transaction history resembles human behavior, and the more points you'll get from each Stamp. 

{% hint style="info" %}
If you did not receive points, it doesn't imply you're seen as a Sybil entity. Rather, it means the model requires more robust activity data to confidently assign points.
{% endhint %}

## Stamp Criteria

The specifics of the model's criteria are kept under wraps to prevent [Sybils](/passport-knowledge-base/common-questions/what-is-a-sybil.md) and other bad actors from being able to manipulate the system. Rest assured, the model is designed to reward authentic, varied, and consistent participation on the network, and has been rated as the best-in-class Sybil detection model in the industry by third-party experts. 

## The 90-Day Validity Period

The 90-day renewal cycle ensures that the Stamp remains a current and accurate portrayal of your latest activities. This regular update aligns with the fast-paced evolution of the Ethereum ecosystem and allows for adjustments that reflect your most recent contributions.

## Deciphering Stamp Levels

The Model-based Stamps are divided into different groups of credentials. You'll notice that one section awards you based on how robust and human-looking your relevant transaction history appears, while others award you based on specific holdings. 

## The Evolution of the Stamp

We're periodically refining these Stamps to more accurately reflect the vibrant dynamism of Ethereum transactions. While previous versions had merits, newer versions of the Stamps embrace a broader spectrum of engagements, ensuring a more inclusive and comprehensive representation of community involvement.

## Need Help?

For more details or assistance with your model-based Stamps, please [reach out to our support team](/passport-knowledge-base/need-support.md). 


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