Michel catalog number 74-85, even in LHU condition, have an nice catalog value of very affordable 9.00 euro, so if You obtain it for 70-75% catalog value, You can say that it is good deal!
But, to find this complete set, with real cancel, on/off really used cover, will be almost impossible task!
According catalog of Mihailo Radicevic, this set in CTO/used condition have little bit higher value of 13.00 euro, and on eBay, someone is offering just one full set for 8.00 euro (add for this 8.00 euro postage cost, payment fee - than You will reach this 13.00 euro Radicevic full catalog value).
Personally, in my part-time dealership of over 35 years, I have some 5 or 6 sets on desk, but it was sold almost immediately and all was in CTO condition.
So, it is "classic", it is engraved, and it is worth to have in collection!
Shortly, Go For It!