The systematic calibration of spine by measuring the degree of bending under the application of a standardised weight appears to have been entirely unknown in historic and primitive archery.
The most common systematic method of shaft selection from a production point of view, where one existed other than empirical testing by only shooting and discarding and by relating the "feel" of a hand flexed shaft to those that flew well, was to select shafts by weight.
This is sensible as a general principle, given that there is a relationship between wood density and stiffness at any given diameter of shaft.
But it is not as precise a measure of individual shaft spine as measuring deflection of individual shafts.
In any case it is likely that subsequent arrow selection would be done by inspection of grain, shaft straightness, trueness of nock, point and fletching and only then subject to the empirical test of shooting individual shafts and discarding those that did not fly cleanly or go where they were aimed.
Of course this system of empirical testing falls down if the archer has insufficient command or understanding of what he himself is doing, since to make any worthwhile judgement about arrow match it is necessary to be able to distinguish between what the archer is doing and what the equipment is doing.
But it does seem likely that this is what a marksman would do.
In the absence of a systematic understanding of spine and what later became known as "the archer's paradox", such inspection and empirical testing is the only practical option, but like our modern precise spine matching, it only has value within the context of the individual archer's ability to derive a real benefit from such activity.
For the less competent, the archer induced variation is very often greater than any benefit derived from precise spine matching.
It is a truism now as it was then, that a good archer will most likely shoot poor equipment better and more accurately than a lousy archer will shoot good equipment.
Some things never change, only the measure by which they are judged.
That the production of livery shafts should have been standardised to some degree is only logical and there is evidence to support this view, but as far as I know very little specific about standards set or the nature of any quality control, although it is known that inspection and quality control of some sort was applied to both regulating the import of staves and the production of bows.
It is logical that a marksman might cull the general stock, selecting for clean straight grain, sound and straight fletching, points well applied and nocks cut true and not overlarge.
He could also enlarge a thin nock more conveniently than reduce one that was too loose, or adjust his serving to suit a standard sized nock, or correct one that was slightly askew if not too large.
He could reset a point or straighten a shank, even refletch a shaft.
But the time so invested would most likely be spent only upon shafts reserved for more demanding tasks.
That a marksman and indeed any competent archer would be selective about his shafts when he could, reserving any "best" shafts for particular use if he had the option is only logical.
But those who were less able might just take the standard issue as it came.
For the primary (or the initial?) task in battle of providing barrage fire at a distance against massed companies of men, judgement of length would be more important than individual accuracy, but realistically there must also have been situations enough that required individual accuracy and not always at short distances, even though a close shot might be more certain.
And in any company of selected men there would always be those who were more accomplished in this respect.
These men one might expect to reserve their selected shafts for particular use and be as capable as anyone else, if not more so, of effectively using the common issue of livery shafts.
Many of those less capable might rely entirely on the common issue of livery shafts.
Rod.