The term stamp (as outlined above) could be used in the past to denote a week where PSRI had been deducted and paid on your behalf. If you had worked 72 weeks you would have 72 stamps - presumably this related to the fact that someone somewhere either had to attach a stamp to a form to show the payment had been made or someone had to stamp a form with ink.
For most people (except perhaps longtime payroll & social welfare people) the term stamp means nothing in this context any more.
As ClubMan indicated you just need to get on to the Welfare people armed with your PPS number and they will be able to tell you how many stamps/weeks/contributions you have and how many you need for a particular benefit.
Note that some recent records may not be up to date, so if you are very close to reaching a threshold you should do a manual check yourself (how many weeks fulltime did you work and how many weeks part time at what contribution rate) to see whether you are about to reach the threshold. The Welfare people should be well used to working through this type of computation.
Also note that for the thresholds it is all/nothing - if you are one week short and you get treatment you will not be covered, but if you wait till the next week (and SW agree you have reached the threshold) you will be covered.
Make sure you have your PPS number (from payslip for example) before contacting SW to save everyones time.
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