[INM@RLM]

Thank you for those clarifications, Sergio. Yes, you're entirely right in your observations on the sequencing of Bf 108 W.Nr. through time.

D-IONO delivered on the Hindenburg as W.Nr. 988 makes perfect sense and fits neatly alongside W.Nr. 987 delivered to Varig in 1936 from the same batch of seven (W.Nr. 987 to 993). All other sources I've seen through the years never identify a W.Nr. for D-IONO. So this - and for those of my particular mindset - is pretty brilliant and exciting stuff.

Grateful please for whatever details you can lay out regarding the source reference(s) linking the Hindenburg D-IONO to W.Nr. 988.

As you highlighted, the linking in Tincopa+Rivas of W.Nr. 1914 with D-IONO and the Dec-36 arrival of this aircraft on LZ-Hindenburg is an error by Tincopa+Rivas.

To be clear, the D-IONO code could indeed have been assigned twice and the second assignment could have been to this Regensburg Bf 108 with W.Nr. 1914. However, that was not the W.Nr. of the D-IONO that arrived on the Hindenburg, which was built in the early days of Bf 108 production, all still concentrated at Augsburg.

I've also recently tripped over the point that W.Nr. 990 from this same batch was D-IRNU and in 1937 became the Messerschmitt company development aircraft for the MeP 7 two-blade variable pitch propeller [Schwarz blades, 2,350 mm diameter). First flight with the new propeller was 8 July 1937. [text Radinger+Schick: Bf 109 A-E (Schiffer) p.128]

With your W.Nr. 988 and J-BACC confirmed as W.Nr 993 that now means we have five out of seven aircraft identified from this mini-batch. Marvellous stuff, considering we are looking back more than 80 years. :-)