A couple of additions to the post on small fonts at https://www.heritagetortoise.co.uk/2022/06/portable-fonts/. The Penrhys font is about 9 kg in weight – I would describe it as movable but not really portable.
We had a very fruitful discussion on the medieval-religion Jiscmail discussion group. Several people posted links to photos of similar patterns on late medieval fonts so we are back to the possibility that the Penrhys find was late medieval. This honestly makes more sense, both of its very battered condition and of the place where it was found. But the jury, as they say, is still out. You can access the discussion even if you aren’t a list member – go to https://www.jiscmail.ac.uk/cgi-bin/webadmin?A0=MEDIEVAL-RELIGION and put portable fonts as your search term.
Another example has cropped up on Twitter – https://twitter.com/Joseamey/status/1535323907745538051 is a cream terracotta miniature font from the South Western Potteries catalogue ‘This font is intended to be placed on the table of Churches Chapels or elsewhere when required for use. It is really about 9 inches in height’ .
Several more examples (without sizes or much in the way of background, but some lovely photos) at https://www.pinterest.co.uk/andrews7322/miniature-church-fonts/ .