Found Collection

Sorry I don't know what Y#71 and Y#72 are, but anyway, post-war 10 yen coins
have all had the same scripting style.  There have been two minor varieties
(ridged edge and then plain edge) but the scripting has all been the same.
Earlier 10 yen coins were made of gold and there were a number of varieties.

Trying to guess what you mean by a change of script, some post-war 5 yen
coins had a brush-stroke script and later ones had a gothic script.  Neither
of these scripting styles is old and neither is regular (well, they're both
regular, but so are tons of others).

If you're having trouble identifying it, and if it's a post-war coin, then
it's surely a 5 yen coin.  All other current denominations have the number
of yen written in western style in addition to the legal tender value.

The character for the yen is different.  The new script for the yen has two
horizontal bars ans three vertical bars. One horizontal bar is at the top and
one horizontal bar is at the center.  Two long vertical bars are at the ends
and on short verticasl bar is at the center of the two horizontal bar.  The old
style is a vertical rectangle with other rectangles (like a dresser with three
drawers) inside.