Here's a partial image of the Microdesign 1/72 I-16 photoetch set. Two styles of late cowling faces are given, one with all 9 small pear-shaped bulges, the other with the one between cylinders 1 and 9 missing:
The absence of the small bulge is also visible in this image from Massimo's type 24 page:
What is the reason for the difference between the two styles? Could it be because of the addition of the speed regulator? In that case it would be missing on all aircraft with the regulator, but I'm sure I've seen photos of aircraft with the rectangular bulge for the regulator cover, and having all nine of the pear-shaped ones, not just eight, as shown above. Maybe it's a field modification?
I'm trying to relate the presence or absence of this very small detail either to specific types, to a specific engine (M-62 or M-63), or to early or late production of the type 24. I've studied the information here on this site and also the detailed description of building the Eduard 1/48 kit here:
https://translate.google.com/translate?sl=auto&tl=en&u=https://www.tapatalk.com/groups/forodemodelismo/viewtopic.php?t%3D8617%26sid%3Dc34773d822b8a6ffb087ec9b303d5461...but with no answer. Does anyone know? Thank you in advance!
John