TransHead - in the US (assuming that is where you are) the use of an engineering stamp does not "certify" or warrant that your design is correct.
What is does is simply identify the responsible engineering professional who did the work.
Read the individual state engineering laws and you will see that most of them (I'm not sure of all) are like this.
For example - in the state of Nebraska the statute reads:
[blue]The application of the licensee's seal and signature shall constitute certification that the work was done by the licensee or under the licensee's control. [/blue]
Another section reads: [blue]The purpose of requiring each architect or professional engineer to acquire a seal is to assist in identification of the design professional responsible for work performed ..."[/blue]
Note that the seal certifies only that the work was DONE by the engineer. There is no expressed certification that the work is correct.
The issue of correctness in designs/drawings only comes up when someone files either a complaint with the governing board or files a lawsuit. Then the engineer is typically held to the industry's "standard of care" (i.e. what other typical, reasonable engineers would have designed in the same situation).
Back to your original question - the use of an engineering seal for a building or bridge is usually carefully stated to be for that one project.
Subsequent uses of building/bridge plans for other projects are usually denied by contract or directly on the plans.
For a design of a "widget" or industrial item of some sort, where the design is up front and then multiple copies of that design are then produced - that creates difficulty for the engineer in controlling the added risk of multiple uses. I am in a consulting firm typically designing one-time buildings but we have had clients come in with a "product" that they want engineered and then will subsequently use our design for many future applications on other projects. Examples such as ICF forms, scaffolding or supports to aid contractors in construction, etc.
Our understanding of this is that the engineer, placing a seal on a design of a widget, is certainly exposed to higher risk as the future use, and mis-use of the product is not under the engineer's control. How you control that risk, and perhaps get paid more for that added risk is a challenge.
Each state also has various statutes of limitations where after a given period of time the engineer is free of liability.
