I look forward to getting things set "right!" As usual, I won't be the most popular person here, but I'll feel much better getting them on track. "Popular" is overrated anyway, right?
Thank you all for your great information and support!
Can i I possibly repeat a few of the things that have been said and with due respect you seem to be ignoring.
a) If an instrument is used to make a decision on a product or process - then it SHALL be calibrated unless by contract you have implemented an alternative.
b) The Calibration frequency depends on your historical usage - and trend / wear patterns.
(In the absence of these, they should be "immediately" calibrated.
The subsequent frequency - you can worry about later! It is not an issue at the moment and wont be for some months!
If the gauges come back - worn (which may not be detectable as you appear not to know the original condition!) then based on the amount of wear, you can guesstimate a time for the next calibration.
If you don't know the original condition - you can at least assume that when the were introduced - they were in specification - and use this as a basis for guesstimating wear.
However - it may be viable to take a representative selection of the gauges for re-calibration after say 4 months - if no wear is detected then you may be able to assume that similar gauges will be OK and subsequently - calibrate a few more after say 8 months. You can then repeat this action on selected gauges until you are able to detect a wear history.
That,s one solution - however if your company still considers such action as too expensive - as they are "checked" against a customer product ( I cannot imagine how this works) you may be able to get your customer to agree, (in writing) that there master product can be used to verify the gauges.
The other question (which may have been asked - but I may have missed) is Are you getting any complaints / rejects from your customer?
So there you have it - some solid things that you can practically implement - or not!