What are the rules for reading numbers before a foreign counter-word?


Is there a rule of thumb for knowing the reading of a number when it is
written in western numerals, and is followed by a loaned counter-word?

For example, how would you pronounce the "1" in `１セット`? My first thought it to
say `「いっセット」`, but as far as I know it could just as easily be `「ひとセット」` or
`「いちセット」`. The [Wikipedia
article](http://en.wikipedia.org/wiki/Japanese_counter_word) does not cover
loan-word counters, and I cannot find anything on this topic.




I'm going to extrapolate the rules for Japanese counters onto foreign-counter-
words.

Extracted from
[Nihongoresources](http://grammar.nihongoresources.com/doku.php?id=counters#idxenglishrules_for_%E4%B8%80_%E3%81%84%E3%81%A1_counting_pronunciation_rules_%E4%B8%80_%E3%81%84%E3%81%A1):

* * *

Rules for 一

  * When followed by a counter starting with a syllable from the か—, さ— or た—column, いち becomes いっ

  * When followed by a counter starting with a は—column syllable, いち becomes いっ and the counter changes to a 'p' sound

* * *

Rules for 三:

  * When followed by a counter starting with a は—column syllable, that syllable changes to a 'b' sound

* * *

Rules for 六:

  * When followed by a counter starting with a か—column syllable, ろく becomes ろっ

  * When followed by a counter starting with a は—column syllable, ろく becomes ろっ and the counter changes to a 'p' sound

* * *

Rules for 八:

  * When followed by a counter starting with a か—, さ— or た—column syllable, はち becomes はっ

  * When followed by a counter starting with a は—column syllable, はち becomes はっ and the counter changes to a 'p' sound

* * *

Rules for 十:

  * When followed by a counter starting with a か—, さ— or た—column syllable, じゅう may become じっ or じゅっ

  * When followed by a counter starting with a は—column syllable, じゅう can become either じっ or じゅっ and the counter changes to a 'p' sound

* * *

In short I don't think it matters if the counter is of Japanese origin or
foreign origin. It depends on the first syllable of the counter.




Following [this advice on
Meta](https://japanese.meta.stackexchange.com/questions/593/comments-are-not-
for-answers), I'm going to throw in an answer I'm pretty sure of, but could be
corrected on.

Scanning down the [list of example counters in the Wikipedia
article](https://en.wikipedia.org/wiki/Japanese_counter_word#Common_counters_by_category)
you linked to, _every one of them_ starts with `一{いち}`, or it's [phonetically
adjusted
equivalents](https://en.wikipedia.org/wiki/Japanese_counter_word#Euphonic_changes)
like `一{いっ}`. There were a lot, though, so maybe I missed one or two
exceptions.

Thus, the rule of thumb I think you're looking for is:

> Unless you already know for sure it's an exception, always guess the counter
> starts with `一{いち}/一{いっ}`

I think this could be said for just about all counters, not just foreign
words. Since you're asking specifically about "loan-counters," though, the
point is that this rule of thumb would encompass them as well.

I can't think of an example exception, along the lines of `一人{ひとり}` and
`二人{ふたり}`, that uses a loan-word in the counter.

