Products / Case study
Mohur
Community
Coin collecting, for people who see history in coins.
A home for your collection, a catalogue of the coins that were actually issued, short lessons on the history behind them, and a community that verifies coins without ever putting a price on them.
- Platforms
- Android, iOS (coming)
- Status
- Open beta on Android
- Built by
- Devian Labs, in-house
- Stack
- Flutter, Dart, Firebase, Cloudflare Workers
01The problem
Most coin collections start by accident: a tin from a grandparent, a coin that turned up in your change. Somewhere along the way it stops being money and starts being a story.
Then the hobby gets hard. Half the coins are in a biscuit tin and nobody remembers what's there. When you want to know if a coin is real, everyone you could ask is trying to sell you something. Collectors had spreadsheets, dealer websites and scattered forums, but not one place built for them.
02What we built
The product.
Album
Every coin you own, photographed, graded and noted with where it came from and why it matters.
Catalogue
The coin types that were actually issued, from punch-marked karshapanas to the first Republic rupee, so you can see what you're missing.
Learn
Short lessons on who struck these coins, when and why, written as history rather than reference tables.
Community verification
Share a coin and fellow collectors vote on whether it's genuine and how it grades. Never a price tag.
Museum
Published coins to browse by period, metal and verdict, with a featured coin every day.
Admin console
A web console where the team writes courses and lessons and sends notifications to collectors.
03Under the hood
The engineering we own.
- 01
Reputation-weighted verification
A vote's weight combines the voter's level, their track record in that era and their role, capped at 8×. Consensus needs two quorums and 70% agreement. A coin with no agreement after six votes is marked Disputed.
- 02
Server-side reputation
XP is recomputed on the server and verified against the user's Firebase ID token. Security rules stop clients from writing their own XP.
- 03
Privacy as a data rule
A coin's public view strips its financial details, and 879 lines of tested Firestore rules enforce the same boundary on the server.
- 04
Private images at the edge
A Cloudflare Worker serves coin photos from a private R2 bucket only to signed-in users, verifying each Firebase token's signature, while keeping URLs stable for the app's image cache.
- 05
Clean, testable layers
Features, data and a pure-Dart domain, with an in-memory backend that can be swapped for Firestore. That keeps 600+ app tests fast.
04Key decisions
Story first
Every screen starts from a feeling a collector already knows, and only then says what Mohur does about it.
No prices in the community
The moment coins are valued in public, the conversation turns to selling. Mohur keeps it about the coins and their history.
Built with collectors
An open beta on Android lets the people who care about the hobby shape it before the wider launch.
Free, with a fair model
Ads support the app and a one-time purchase removes them. No subscription.
05Where it is today
Open beta on Android
Mohur is in open beta on Android: join the testers group, opt in on Google Play and install it like any other app. iPhone comes later.
For your project
Need something like Mohur?
The team and the engineering behind Mohur are available for client projects and long-term partnerships.
Mobile apps
Android and iOS apps in Flutter, offline-first when it matters, with payments and store releases handled.
Web applications
Products, dashboards, admin consoles and storefronts in React and Next.js, fast and search-friendly.
Backends and APIs
APIs, auth, databases, sync engines, security rules and edge workers, designed to be secure and cheap to run.
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