That certainly looks like a 19 litre to me, whether or not it has wrinkles. I have to say that to me, from the picture it looks to have VERY faint wrinkles in the underside, even if they don't show through the top.
Wrinkle tanks definately fitted through into the die cast bikes - I have had them on 1008054, 1008612, 1010802, and even a 1015xxx bike (of course can't often be 100% that Honda put them there!).
My #5298 came to me in 1990 with what appeared to be its original tank (blue green exact match to fork ears and headlight shell), but no wrinkles on underside. So, what to conclude - in spite of its apparent originaility that probably that something happened early on in its life that lead to the tank being replaced with NOS.
Let the debate rage!
Cheers - Chris R.