Rover, Lloyd, Steve, thanks for the comments. I've attached a picture of the obverses as Steve asked.
Per the terminology at Mr. Goldsborough's site:
http://rg.ancients.info/owls/the tetradrachms on the top row are all Intermediate
Style owls (haven't yet attempted to classify further)
with a classical (?)
drachm, a Classical
Owl (
type A given the more obvious
incuse square? I confess I haven't delved into the subtleties of
Athena's portraiture), and two other Intermediate
Style owls. I've seen some similar intermediates described as "Pi
types" given the pattern of the scroll on
Athena's helmet.
For those who are interested, the tets on the top row weigh:
17.2g 17.15g 17.13g
respectively and those on the bottom weigh
3.74g (
drachm) 16.96g (Classical) 17.18g and 17.19g respectively.
As is no doubt obvious to the
owl cognoscenti, the Classical
owl, despite having a noticeably larger
diameter, has a thinner
flan, and weighs a couple of centigrams less, possibly in
part due to the severe deformation (and loss of mass?) from the violent
test cut. Thankfully, in this case the test cutter chose not to bisect the
owl. (Which I understand may have been done because the
owl's beak was among the thickest portions of the
flan).
Amazing feeling looking at these, and contemplating whose
hands they may have passed through over the years. The rightmost intermediate-style
owl on the bottom row has a strange crystalline encrustation on the
reverse that I've asked for suggestions on before over at the cleaning board--careful application of lemon juice+distilled water was suggested. I have not yet
had time to experiment, am hopefully looking forward to seeing the
owl awaiting underneath.