Pls advise which pass is most appropriate

Hello cas80, and welcome! A Eurail Select Pass is meant for travelling in 3 to 5 European countries. You'll only be visiting 2 (Switzerland and Italy), so this isn't a good option. You could consider a Eurail Flexi Pass, which provides 10 consecutive days of free travelling throughout Europe, which could be used for your train journeys in both Switzerland and Italy. However, your travel distances within Switzerland are mostly short and therefore not that expensive, so a Eurail Flexi Pass wouldn't turn out to be an economical solution. You can better purchase a pass that covers Switzerland and buy regular tickets for your trips in Italy, or use an Italy Pass there. According to my calculations, you're best off with a Swiss Half Fare Card for your trips in Switzerland. The Swiss Half Fare Card costs only CHF 99.00 and provides a 50% discount on all Swiss trips you mention. The Swiss part of your journey from Interlaken to Venice is discounted by 50% as well, as your Swiss Half Fare Card is valid up to the Swiss border station (which will probably be Domodossola).

Seat reservation is only necessary for international trips, so you should reserve seats for the train journey from Interlaken to Venice. If you arrange for this using the online timetable, you can indicate that you have a valid Swiss rail pass. This way, the discount for the Swiss part will automatically be calculated in the price. To do this, get to the Swiss timetable, fill out Interlaken Ost as your departure station and Venice as your destination and pick the correct date. Next, choose your preferred connection and click 'Fare/Buy'. You'll enter an ordering process, in which you'll be asked if you have reduction options for Switzerland. Pick 'Half-Fare travelcard 1/2/3 years' from this drop-downlist, as this provides a 50% discount too, just as the Swiss Half Fare Card.

I hope this provides some answers! Kind regards,