An "Exhibition grade" W. Collath of similar construction on Guns International is valued at slightly below 3K. This of course is dealer's asking price, not a realized sale price.
The J.Specht seems to be in lesser condition. The 68 cm barrels were not overly common at the time (except on combination guns) so I would carefuly check about possible shortening. Also I can see no information about the condition of the bores which of course is crucial. Last but not least, W.Collath is a well known brand name, not so J. Specht. So, for the time being, I would not dare to value it over 1K.

With kind regards,
Jani