Nice bike konakai.

This is definitely the Austrian RIH. RIH in this case stands for Rad Industrie Hamedl (or "Radindustrie Hamedl") from Vienna. There were 5 Hamedl brothers (Hans, Leopold, Franz, Karl and Friedl) who were all involved with bicycles and racing in some form but it was Franz who started the RIH.

The only explanation of their frame numbering that I've come across was from Michael Zappe, one of the authors of the book titled “Wiener Mechanikerräder” (that I'd love to get btw).
While decoding ":1867997" he explained that colon stands for Reynolds 531, "1" is for the road race geometry, 8 for 58cm frame size (ctt) and the rest was "the number." He then said that if you subtract 11 from 67, you'd get the year of production (1956). It wasn't clear where this "11" came from.

So, using this decoding, :1569740 would give you a 55cm road racing frame made of Reynolds 531 tubing, built in 1958. This year of production aligns with the excellent parts assessment by juvela

Btw, that seat tube sticker reads "Modell Extra Leger":