Feature spec
Goal: Send a clear invoice after finishing a job.
- Add a client, line items, a due date, and payment instructions.
- Preview the total before exporting a PDF.
- Keep an editable draft if export fails.
Greysheet: Coin & Currency Pricing
Free
Evidence scope: No current overall US chart position is available. Category-chart positions shown in discovery are a separate scope. Revenue is a directional model estimate, not verified earnings.
A product spec, screen plans, and build steps for your coding agent.
First kit free with a verified email
Combine features and design from your favorite apps.
Your first Build Kit is free with a verified email.
Generating… usually about a minute.
What should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
A product spec, phased build plan, differentiation notes, and screen references.
Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Goal: Send a clear invoice after finishing a job.
Invoice editor: Client at the top, editable line items in the middle, total and preview action at the bottom.
States: Empty draft, validation errors beside each field, exporting, and a retry action that preserves the draft.
Hypothesis: Contractors need faster repeat invoices more than more templates.
First experiment: Test duplicating a previous job with five contractors. Watch where they hesitate before expanding the feature set.
The full kit adds a phased build plan, evidence notes, tool prompts, and implementation guidance. It is a plan for your coding agent, not a finished app.
Usage: Mechanics are fair game; never reuse the original name, branding, assets, or verbatim copy.
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Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
Rork plan preview for Greysheet: Rare Coin Pricing: map the core Reference workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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These are generated suggestions, not verified review quotations. Check current App Store reviews and speak with users before treating a possible gap as a requirement.
Hypothesis 1
Assumption to check: Expensive subscription
Validate with people who use this workflow before building.
Hypothesis 2
Assumption to check: Missing features
Validate with people who use this workflow before building.
Hypothesis 3
Assumption to check: Poor performance
Validate with people who use this workflow before building.
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
Greysheet: Coin & Currency Pricing Trusted by dealers, investors, and collectors worldwide, Greysheet is the industry standard for pricing and catalog data in numismatics. Our FREE app delivers professional-level pricing and research tools for anyone serious about coins and paper money. A paid companion subscription is required to access pricing in the app. For over 50 years, Greysheet has been the undisputed authority on U.S. and world coin and currency pricing. With hourly price updates, you can rely on the most accurate wholesale and retail pricing available—across all grades, mints, and varieties. Greysheet continues to expand its coverage to meet the evolving needs of the numismatic community, offering transparent, market-driven pricing backed by real auction data. Backed by Whitman Brands Greysheet is published by Whitman Brands, the world’s leading numismatic publisher and the parent company behind trusted resources including Greysheet, Greensheet, Red Book, Bank Note Book, Friedberg, and more. When you use Greysheet, you’re using the same data professionals rely on every day. What You Get 1+ million wholesale and retail prices 2.5+ million auction records from major auction houses 8+ million high-resolution images Coverage across U.S. coins, world coins, and paper money App Features Complete listings with all relevant mint marks, grades, and designations Wholesale & retail pricing for: U.S. coins (Greysheet & CPG) World coins (Greysheet & CPG) U.S. paper money (Greensheet & CPG) World bank notes (The Banknote Book) Auction prices realized Gold, silver, and platinum spot prices Industry news Events directory Dealer directory U.S. Coin Series Covered =================== Colonial & Post-Colonial Coinage, Half Cents, Large Cents, Flying Eagle Cents, Indian Cents, Lincoln Cents, 2-Cent & 3-Cent Pieces, Shield Nickels, Liberty “V” Nickels, Buffalo Nickels, Jefferson Nickels, Half Dimes, Dimes, Quarters, Half Dollars, Dollars, Gold Coins ($1–$20), Classic & Modern Commemoratives, Proof & Mint Sets, Hawaiian Coins & Tokens, American Silver Eagles, and more. (Full coverage includes all major types, varieties, grades, and mint marks.) U.S. Currency Covered =================== Colonial & Continental Currency, Demand Notes, Legal Tender Notes, Treasury Notes, National Bank Notes, Federal Reserve Notes & Bank Notes, Gold & Silver Certificates, Fractional Currency, WWII Emergency Issues, and all major small- and large-size U.S. paper money types. World Bank Notes Covered =================== Over 310 countries covered with exhaustive detail for each issuer and bank note. World Coins Covered =================== We are growing our coverage of world coins with an early emphasis on Canada, Mexico, UK, Australia, and modern issues. Subscriptions =================== Greysheet pricing is available through auto-renewable subscriptions billed to your Apple ID. Plans renew monthly or annually unless cancelled at least 24 hours before the end of the current period. Manage or cancel anytime in your App Store account settings. Terms of Use: https://www.greysheet.com/terms-of-use Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Privacy Policy: https://www.greysheet.com/privacy-policy
Written user reviews are not shown here. Check current App Store reviews >
Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
Not assessed in a Build Kit yet.
A reliable timeline needs an agreed scope and a technical check. Ask your agent to estimate the phases in BUILD_PLAN.md after that review.