Instructions
1. Load Stamp Scan
Click the button to load a scan or photo of a single “patient” Type I or Type II 1851–57 3¢ Washington stamp. PlateAI handles both imperforate (#10, 10A, 11, 11A) and perforated (#25, 25A) stamps equally well. It was not trained on Type III or IV stamps (#26, 26A) and will return meaningless results if you attempt to plate one.
For best results, use a 1200 dpi flatbed scan. Higher resolutions are accepted but provide no accuracy benefit. Lower resolutions and cell phone photos are accepted, but accuracy degrades with image quality.
2. Align and Crop
PlateAI aligns all stamp images to a common orientation before analysis. It does this automatically by detecting the centers of the rosettes. Automatic detection works on most stamps. When it works, you’ll see colored crosshairs overlaying the four rosette centers and a yellow box connecting them. If the alignment looks correct, click “2 — Align & Crop.” An aligned and cropped version of your stamp will appear in the left panel; click it to view full size.
Automatic detection fails most often when cancels obscure two or more rosette centers. When that happens, one or more crosshairs will be misplaced and the yellow connecting box will appear skewed. Click “Mark Rosettes Manually” and then click the four rosette centers in clockwise order: Top Left → Top Right → Bottom Right → Bottom Left. Once all four are marked, click “2 — Align & Crop.”
3. Plate the Stamp
Once aligned and cropped, your stamp is ready to plate. No attribute selection is needed on a first attempt — just hit the button. If PlateAI doesn’t find the correct position on the first try, you can narrow the field by selecting known stamp attributes in the left panel.
4. Interpreting Results
PlateAI returns a ranked list of the top 10 best-matching positions for your stamp, showing the plate, relief, type, and Scott number for each candidate, along with a similarity score between 0 and 1. This score is the cosine similarity between your stamp’s feature embedding and the reference embeddings at each position — higher is a stronger match.
The results header shows the top predicted position and Scott number, each with a confidence level: HIGH or LOW. These levels are based on both the raw similarity score and the gap between the #1 and #2 candidates — a small gap means two positions are nearly indistinguishable to the model, which warrants caution. Poorer quality stamps and stamps with missing margins will tend to produce lower confidence results.
Accuracy on the 455-stamp test panel by confidence level:
- HIGH — 100% accurate
- LOW — 84% accurate
A LOW result does not mean the top candidate is probably wrong — most LOW results are still correct. It means mistakes will slip through unless you verify with visual comparison. Treat the top candidate as a starting point and use the Compare feature to confirm.
The Scott number prediction considers all 10 top candidates, not just the top result, and is typically HIGH even when position confidence is LOW — the model may know the general plate family without being able to resolve the exact position.
To copy results to the clipboard, click Copy. To log results across multiple stamps in a session, click Log — the current stamp is logged immediately. Download your session log as a .csv file by clicking CSV.
When session logging is on, each candidate row gets a radio button to mark it as your choice. The Compare modal also has a Log as my Choice button. Your selection is saved to the session CSV in the log_choice column, useful for batch-processing where you want to record your final answer without retyping it.
5. Compare
Once results are returned, click Compare on any candidate to open a visual comparison window. Your patient stamp is shown in color (if your scan was in color) alongside grayscale reference images from four vetted collections: Chase, Amonette Historic, Celler, and Lund-Amonette-O’Doherty (LAO). All images — patient and references — are cropped and aligned identically, making direct comparison meaningful.
Three tabs offer different comparison views:
- Corners — the four corner regions, where many position-distinguishing features appear
- L/R Framelines — left and right frameline strips, shown as 10% compression scans alongside full uncompressed strips
- Top/Bottom Framelines — top and bottom frameline strips, same format
- Full Stamp — your patient and a reference shown side-by-side at full stamp size; cycles through all four collections
Click any image to zoom to 200%. Use the arrows at the bottom to move your patient stamp next to whichever reference you want to compare against. Use the arrows at the top to cycle through the top 10 candidates. Full-size zoomable views of each reference stamp are available from the header of the compare window. Known position attributes (recuts, guide dots, anomalies) are shown for each candidate.
6. Refine
Most stamps will plate correctly on the first attempt without any attribute selection. If the correct position doesn’t appear at the top of the list, specify what you know about your stamp using the basic attribute filters in the left panel — color (Orange Brown or Not Orange Brown), Type (I or II), Relief (A, B, or C), and Plate. For finer filtering, click Advanced to specify recuts, guide dot locations, plate anomalies, and margin position.
Two actions use your filter selections in different ways:
- Apply — narrows the results list to hide candidates that don’t match your selected attributes. Does not re-run identification. If no candidates in the current list match, the list will show that no positions match and you can click Plate! to search more broadly.
- Plate! — re-runs identification with your current filter selections, returning the top 10 matching positions from the entire field of 2,600. Use this when the correct position isn’t in your current list at all.
Both Apply buttons — the one on the basic panel and the one in the Advanced modal — work identically and consider all filters (basic and advanced) together. Note that PlateAI has no built-in ability to predict relief — selecting the correct relief typically has the largest impact on narrowing results when initial confidence is low.
7. Position Explorer
Position Explorer is a reference tool, entirely independent of PlateAI’s AI identification capability. Use it to browse all 2,600 plate positions across 13 plates and compare reference stamps from the four vetted collections — with or without a patient stamp loaded.
Select a plate from the dropdown, then click any position to open the Compare window for that position. Use the attribute filters in the left panel (basic or advanced) to narrow which positions are shown as eligible — ineligible positions are grayed out and not clickable. The match counts at the top of the explorer show how many positions pass your current filters, both for the selected plate and across all plates.
If a patient stamp is loaded and aligned, it will appear alongside the reference stamps in the Compare window. You can load a stamp at any time without plating it — Position Explorer does not require the stamp to be identified first.
