What color is a ' Natural ' lamp (here 'Natural Sunlight' is 5000k) your pic looks closer to 3500k?

I think it is 4000K

@ XmasLightGuy similar to your Cool White Deluxe! Around the 4000K as mentioned.

There can be a bit of pinky reddishness to the light too...

Very Nice! Rare lamp, Could do with TL8 on here to date this!

I've seen this working in a T12 Pop Pack! It looks awesome! A nice colour that was killed off by the likes of triphosphor 840! Natural was favoured by many large retailers for it's reasonable colour rendering properties leading to enhanced product appeal! As seen in stores like Woolworths and Rumbelows! Yes a date would be nice. I'll take a guess at 1973?

nice old crompton tube there, even better that its a rarity in colour also. Those endcaps look like philips ones?

@ Arrowslim yep I believe there was a 'gentleman's agreement' between Crompton and Philips. Crompton would make the fittings and Philips would make the lamps. Hence you got identical products from both brands! That's my reckoning if someone could confirm this?

Yes I think think it is, Crompton certainly haven't made any of their own lamps in decades or at least not fluorescent and discharge ones. The etch looks rather Endura like to me although the caps are as said, Philips style!

Date code hard to read on this pic - if it's "4B" then it's Feb 1974.