How to interpret 過去数十年分


I'm looking for some help in understanding the second line below as I'm not
sure I've understood it correctly. Is it saying that the jeweller mentioned in
the first line was commissioned to perform jewel appraisal for the last
several decades? I'm a bit confused here as to how 年分 works.

「例の偽ダイヤを集めてた宝石商は？」

「はい。やはり過去数十年分のジュエル鑑定を市から委託されていました」




It's "several decades' worth of appraisal" - the implication is that there is
a certain amount of work to be done every decade (of appraising jewels), and
the amount does not change much decade by decade, so you can count them by
decades.

The frequency is unclear from the passage alone, by the way. It's possible
that they did the appraisal only once in those decades in one big batch
(perhaps unlikely), once every year, once every month, or more frequently than
that.

A similar and more common example: If you get garbage collection every week
and the collector skips one time, you will have accumulated two weeks' worth
of garbage, or 2週間分のごみが溜まっています.




It's "several decades' worth of appraisal" - the implication is that there is
a certain amount of work to be done every decade (of appraising jewels), and
the amount does not change much decade by decade, so you can count them by
decades.

The frequency is unclear from the passage alone, by the way. It's possible
that they did the appraisal only once in those decades in one big batch
(perhaps unlikely), once every year, once every month, or more frequently than
that.

A similar and more common example: If you get garbage collection every week
and the collector skips one time, you will have accumulated two weeks' worth
of garbage, or 2週間分のごみが溜まっています.

