All E-Type dip sticks have an E stamped on them and it does not stand for

'Empty'
It is there because it is specific to the E-Type engine, or more correctly the sump design, so no substitutes. The chequered area represents the oil high and low marks so as long as the oil is in that region you are OK. Ideally you should use 20W/50 mineral oil from one of the refiners 'classic' range. Two things to consider:
1. Do not overfill as the big ends will strike the oil and cause it to froth resulting in oil starvation damage
2. After draining the oil/replacing filter refill with the correct measured amount (15 imperial pints, 18 US pints, 8.5 litres) which will give you the correct level on the dip stick for future reference
3. Make sure the dipstick is perfectly straight from the cap downwards otherwise it can route itself behind the sump baffle giving a wildly incorrect reading
4. There should be a felt seal under the dip stick cap and many are missing. Available from the usuals as part C.17585