Thanks for getting back to me. Looking at these, I don’t think they are older than the 20th century. The bases are unmarked and unfinished. The craftsmanship, particularly the shapes of the eyes and nostrils and the patterning of the white knobs, indicate more recent design and mass production rather than one-of-a-kind artistry.

Here are links to similar items I found. Many are from the 1970s. It seems like the style is Italian and/or related to Jean Roger, a French designer.

I found a few completed online sales and asking prices below and my estimate is based on those. Note that the estimate is for the pair.

$326 asking
https://www.chairish.com/product/1695818/20th-century-vintage-italian-glazed-frog-planter?gclid=Cj0KCQjw8IaGBhCHARIsAGIRRYpSiqC8QMhoI-t_xO-8J5cyI2K9L81B32OUiHOiOC6jF12eyQOkSVsaAl3bEALw_wcB

$249 asking
https://www.rubylane.com/item/1836869-Vintagex20Hobnailx20Frogx20Pla/1970x27s-Vintage-Hobnail-Frog-Planter-style?gclid=Cj0KCQjw8IaGBhCHARIsAGIRRYqjKvATgHFJbH2ueBnNKKSc9Ke1Pojr86QsfwCB6MM7pum9_d4OGisaArovEALw_wcB

$46 asking
https://www.etsy.com/listing/1024928117/vintage-mid-century-hobnail-style-white?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=hobnail+frog&ref=sr_gallery-1-1&from_market_listing_grid_organic=1

Unknown price, but interesting descriptive info
https://www.chairish.com/product/2631969/vintage-1970s-jean-roger-style-white-hobnail-ceramic-frog-planter

Sold for $85 on ebay
https://www.ebay.com/itm/203439271809?hash=item2f5decef81:g:Z0AAAOSwdHdgffUS

Sold for $160 on ebay
https://www.ebay.com/itm/164361135158?hash=item2644afe436:g:BsYAAOSwLLRfTD47

Jean Roger frogs $200-$900
https://krbnyc.com/inventory/frog-planters-by-jean-roger/