Sorry for the delay in response, the cannon was a little tricky to track down.
(1) Hausser "Elastolin" Norman knight [Figure #8880]
Elastolin is the trade name of the Stuttgart company O&M Hausser -for Otto & Max Hausser whose father Christian Hausser founded the company in 1904. They first issued this range of medieval knight figures (Ritterfiguren) in this hard polystyrene plastic in 1955. Pre-World War II versions were made of a sawdust-filled composite.
This equestrian figure on a rearing charger wielding a mace is in the 1/24 scale size, known as a "70mm" scale (7cm) because the rider is approximately 7 cm or 3" tall (where the average height of a man is taken to be 168 cm, so 168/7 = 24 thus 1/24 scale).
This 1960s vintage painted knight in the 77mm scale sells on line in the range of $35 - $75. This example sold for $70.
Full retail/insurance value: $150.
(2) Hausser "Elastolin" Medieval Haufnitze (Howitzer) gun
This is also by Hausser and is model number 9800.
A replica of a 15th century siege weapon and the forerunner of the modern howitzer (between a mortar and a cannon).
This example in its original box (proving that it is indeed a Hausser/Elastolin) sold on line for $80, which is about the the top end for one of these.
So yours would have an eBay range of $50 - $85.
Full retail/replacement/insurance value: $170.
Hope this does the trick.