BSA made approximately 468,447 (Skennerton) No I MkIII* in 1917 so you have one in almost half a million. It is not likely to have scarcity value.
Observed prefixes for serial numbers from BSA in 1917 are D, E, F, G, H (Stratton) - if you do not have one of these look for signs of FTR (although this is not an absolute given these are observed data)
HV indicates sighted for the MkVII round, common mark
If it had an H in a circle on the barrel this would indicate a heavy barreled "sniper" - very uncommon, mostly post war and mostly Australian.
The simple answer regarding the value of the rifle is "whatever the market will bear" my gut reaction on "do you have an especially valuable rifle?" is...NO.
All matching numbers are however a plus, (does this include the front sight protector, the wood furniture?) - is the bolt "force matched " to the receiver/barrel? (ie does it look like the rear of the bolt handle has been filed down and renumbered- pretty common)
The fact that it is drilled and tapped for a scope (unless it is a military fitting - vary scarce without other indicative markings) is a major negative in collectors terms. If the drill /tap can be shown to be original to the rifle (ie it is a "sniper" rifle) then we are into another set of figures but frankly I would think it very very unlikely. (although not impossible)
In terms of value you omit lots of important information: What is the condition of the bore? How is the headspace? what about the overall condition and match of the wood (does it have a transverse reinforcing screw through the fore end?) these are all potentially significant elements in valuing a rifle.
In the US I would expect to pay between $150 and $250 for a rifle meeting this basic description. In the UK because of the license requirements (and exchange rate!) it will vary (it seems deactivated weapons sell for a good deal more), same for Canada etc. of which I have no knowledge. The drill/tap probably kills the historic value but if someone is interested in a 1917 BSA for idiosyncratic reasons then they may well pay more. If you were selling to a dealer whose aim was to sell on you would very likely get the low end of my bracket because the dealer has costs associated with documentation, transfer and then resale at a profit so...value? virtually impossible to determine. Weapons/Artifacts have no intrinsic monetary value they are worth what people will pay for them. In my local gun shop this would probably be tagged at $250 but you may be able to get it for less - Condition is important. Individual rifles may have historical significance (which may or may not translate to monetary value) regardless of their condition. (so for example weapons of known provenance, unit marked etc may be of higher value even in poor condition) but these are uncommon outside specialized collecting circles.
So the bad news is - you have a common rifle which has probably been modified since it was sold out of service. Historically it is of little significance. It probably shoots well (if in sound condition).
The good news (in my humble opinion) is more or less the same! the drill/tap is a negative if it is non military (which 99% are) but, disregarding that, you have a standard SMLE no1 MkIII* of the type that armed the British and Commonwealth forces from 1916-1942/3 (and on) in good condition it is an accurate and very reliable rifle. Although purists will shudder, the idea that someone wanted to add an optical sight more recently is in my view testament to this, over a century after the rifle was introduced it is still an effective weapon. Historically is it unique? no - but of course it was designed as a mass produced weapon for a mass army so why should one expect that? When you shoulder it, or sight it down the range you are doing what (literally) millions have done before in numerous circumstances before you, and that, even if it does not imbue it with monetary value in a fickle market, certainly establishes some form of historical connection.
There are several books (Skennerton or Stratton) which have lots of detail should you be interested and a good number of web sites too.
Pictures would help members comment as to general condition etc.
Hope this is of use
Thanks for your help .It does shoot very well and has become a faithful deer rifle