1. There are two large starter holes in each airwell. That's the channel with the dogleg. With a good light, and preferably with the drills or pin gages, check if there are holes drilled in the bottom of each one. They should be around .026 to .027" diameter. If the e-holes in the channel are bored through, then odds are there is no emulsion tube.
2. Look at the top of the meter block. See if there are cups or flat caps sealing the drilled wells. The inner pair are the main wells.
3. Remove the main jets and peek into the main well. Sometimes the bottom of the tubes are visible.
