I generally collect Greek coins, so I don't have much experience in sestertii, however, it appears that he tooling and smoothing on the above two coins does not appear to chilled the bidding much.
I know we don't talk prices here, but by what percentage do you think the price of a coin that has been lightly tooled, smoothed and filled, like the Agrippina above generally be affected by such treatment? This one appears to be well done. Would it sell for more than a cleaned but untouched coin that is worn and pitted?
And if so, is that what's leading to so many coins being tooled, smoothed and/or filled?
It also appears that smoothing is generally accepted now as part of the "restoration/conservation process" Yes? No?
Is tooling getting to the point where it is acceptable?
What about filling, like the second coin? It seems to me that taking a pitted coin and filling it with whaterever people fill these with, goes above and beyond what should be acceptable?
How easy is it to detect filling if it's not disclosed?
The current auction house is disclosing, but I always wonder whether the person who sells the coin next will disclose.
Tooling, by which I mean non-accidental metal removal, reduces the inherent value of a coin. It becomes a less valuable historical document. This is axiomatic. It may not reduce its market price, in fact it may increase it due to competition between naive collectors. However, sometime in the future when the purchaser of a tooled coin sells, the price may well revert to normal, i.e. a lower price than would be fetched by a well-cleaned but not tooled example. (And this is the comparison that should be made - against another expertly cleaned example, not against an uncleaned coin)
If smoothing deliberately removes metal, it is tooling. The same applies. Sometime down the road, a serious collector or student will place a lower commercial / historical value on a coin that has had metal removed.
I can assure you, from speaking to other serious collectors and numismatists, that if there is a shadow of uncertainty over a coin, as regards tooling or smoothing, then they hold back on their bids. There was a classic example in a recent high-end sale involving two rare sestertii. That which had obviously untouched surfaces fetched a much higher premium over estimate than the coin over which there had been some debate. I handled both coins, neither looked to be tooled though one was more evidently cleaned to the limit and perhaps rubbed a little vigorously in the process, but no evidence of any attempt to alter or improve the coin. However, although not my area, I concluded that the uncertainty alone on the 'smoother' coin would cause me to hold back on bidding, and correspondingly that I would place a high (commercial as well as academic) value on the clearly untouched - save for cleaning - surfaces on the other coin.
Expert cleaning and restoration, that is sensitive to potential risks of a coin appearing tooled or smoothed, increases the value of a coin and also its price. It's value as an historical document is increased because the document has not been damaged, but has been conserved in a much clearer condition.
If what is removed by smoothing is just a combination of non-patina deposits and some patina, and there was no deliberate attempt to remove metal, and the end results is, cosmetically, a coin which could have arrived in this condition by wholly natural means, then it counts as cleaning. However real experts will know whether the coin has passed the "wholly natural means" tipping point, and once you go too far you can't reverse.
So, hold off on the dental tools. Minor surface deposits or corrosion effects, perhaps slightly obscuring a few letters and/or making the field less uniform, can act as a form of guarantee of no-mechanical alteration, and hence increase the coins value (NB of course some crudely tooled coins are repatinated to try and create this effect but really fool no-one).
Filling: this is not removing anything from a coin, and if clearly marked and if 100% reversible, has no long term implication. It's a cosmetic matter, a commercial matter, and a matter of disclosure. It is a market matter. It has no relation to a coin's numismatic value. However if an expert thinks, from its surfaces, that a coin has been filled then he will of course wonder what is real and what is not real, and will hold off bidding, and may exclude the coin from studies.
Disclosure: if properly disclosed and accurate, then remarks on tooling, polishing, smoothing, filling etc. can only increase the respect a coin is held in by those with expertise, to the extent that it provides assurance that the coin has been closely looked at and that there are no other issues.
Market value of tooled, smoothed, polished, filled coins, when disclosed properly: who cares? It's not important in any real sense except to the purchaser, who has bought a coin recognising these defects. If two naive collectors choose to place a higher value on an altered coin than an unaltered coin, well, it happens, and one of them will win the coin but may be upset in future years when others don't value the alterations as much.
Market value of such alterations when not disclosed? If the alteration is evident, then it's just a matter of choosing whether to buy from such companies. It's a market issue (choose your marketplace well).
If there are borderline judgement between well-cleaned and smoothed, then the market will take care of it, as in the above cited two sestertii example. It's a market issue (how you value one coin)
Finally, remember that price often has no relation to value.