A third-party seller on Amazon or eBay was including sheets of suspicious US postage stamps in product shipments, unsolicited, with full-color glossy notes offering more stamps in exchange for positive reviews.
(I took the stamps and note I received to a post office, where a manager agreed they looked suspicious, and I asked them forward it up the chain. I like the USPS as a trustworthy service and institution, and I hate counterfeiting.)
The USPS is also, ahem, rather incompetent, and their own report [1] shows that "mitigation efforts are limited, with no substantive approach to identify counterfeit stamps in the Postal Service network. While the Postal Service and the Postal Inspection Service have increased prevention-related efforts, the quantity of counterfeit stamps in the network remains unknown."
So the increased value of the stamps, the inability to change old Forever stamps, and the lack of enforcement have created a perfect storm for the counterfeiters.
[1] https://www.uspsoig.gov/reports/audit-reports/counterfeit-st...
https://www.royalmail.com/sending/barcoded-stamps
There are still some "Forever" stamps (those with pictures on or Christmas Stamps) but the old non-QR code non-forever stamps stopped being legal a while back (but you can always swap them for the new ones for free).
I've had people try and reuse a QR-coded stamp, you just get a postcard saying there's an item of mail with invalid postage for you to collect (and pay for). You get to look at it before you decide whether to pay the fine or not and then your argument is with the sender to reimburse you or not.
I would assume that the tracking number has the address details tied to it (I mean, based on support claims with USPS it definitely does), but maybe there's some obscure package type where destination is not distinct and they abuse that in a pool with other sellers, then at the last mile it gets sorted appropriately?
Seems wild that this market even exists considering how USPS flat rate postage exists.
Was your package something heavy or extremely light which makes weight-based shipping more economical?
If you generate a random number even fitting the pattern and looks like a real one, the scan will fail with an error and fail to register tracking information every single step of the way that package gets scanned from dropoff at the retail postal office (this was the case) as bulk inbound pickup from USPS are only allowed for USPS verified partners.
Label creation (which generates the tracking number) is a billable action in their API. Some volume partners have pre-arranged/allocated tracking number segments assigned to the bulk volume partner/shipper (similar like how IP address v4 is assignment from IANA). And that pre-allocation tracking number range requires $$$$ contract in place. Billing that is post paid like cellphone bill.
Most retail shipping software (like shipengine, pirateship etc.) bills using the prepaid method, meaning you will have to pay for the label at the time label is generated.
Disclaimer: I used to work for a carrier that integrated a few dozens of global shipping carriers.
The tool I bought wasn't what you'd think of as a small, inconsequential item. I'd wager it was ~2lbs and was a automotive brake bleeder in a blowmolded case. Probably the size of an old-timey encyclopedia. Cheaply made of course (almost certainly an aliexpress item). The seller I bought from has what appears to be an aliexpress dropshipping supply chain -- they buy the tool for $, ship from a US warehouse in Florida for $$.