Hi,
Yes that is Thiersch holder. According to the info which was given by Thiersch, ideal height originally in U47 was 58 mm.
For the holder which is in picture you do not need the platform at all, but there are different holders with different heights on a market, so this is why I'll put 2 platforms to the kit, that you could make the height as closer to 58 mm as possible.
Kind regards,
Andrew