It is either a Bach TB502B or a Bach TB503B.
The 502B has a .525" bore and an 8" bell.
The 503B has a .547" bore and an 8,5" bell.
It is listed in our catalogue from GEWA (the distributor of Conn/Selmer for the Netherlands). Recommended retail price (for either) is 796 euros. I haven't had a chance to play it, so can't comment on the quality.
You can find more information here:
https://int.gewamusic.com/product/17831/bach-bbf-tenor-trombone-tb503b.html
The TB450B has the extra brace and is listed (recommended retail price) for 1651 euros in our catalogue. It is mentioned that this model is "Made in Germany". No mention about the country of origin of the 502/503, so we can only guess.