No, a Marlin 881 stock cannot fit in a model 81. The stock would fit an 881, not an 81.
Roughly 150-200 if like new around 110-150 if showing some amount of wear.
model 881
The Marlin Model 1881 was Marlin's first lever action rifle. It fired much more powerful loadings that the Winchesters and it beat Winchester's Model 1886 to the market by 5 years. Condition is everything in antique guns. If it has been refinished, the collector value is very low. If it is in original condition with the expected level of wear but not abused it could get upwards of $2000. THe Model 81 was a .22 cal. bolt action rifle with a tube magazine. It was superceded by the 881 and the the 981. It sells for around $100-200, depending on condition. A good average price is 150-175
It all depends on the condition, I could see it selling anywhere from $85 in poor condition, to $200... but not much more than that.
33% of 881= 33% * 881= 0.33 * 881= 290.73
It is 881, itself.
881 = DCCCLXXXI
881 is a prime number. Its only positive integer factors are 1 and 881.
881 is the 152nd prime number.
881 x 1
Impossible to answer without a descriptio of ALL markings and who made it.