You can guesstimate. The 44 gal mark may be at the ridge, just below the top lip. Go down half way and up an inch or so and that will be 22 gals. Divide the lower and upper halves by half and you will have the marks for 11 gals and 33 gals. There is the possibility that 44 gals is the actual capacity to the top lip so those marks will be very close to 10, 20 and 30 gals with 40 being at the ridge.
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