Service engine and blocks came from a TWO different sources.
1. some were purposely built for parts inventory for the parts warehouses.
2. Bare blocks would have bare V.I.N. pads and the top I.D. pad may or may not have been stamped with an "S" and may or may not have been stamped WT or TW for water test. They would have no other stampings on them.
3. Short blocks will have a bare V.I.N. pad. e.g. 440 engine The top I.D. pad will have either S440 or 440 if it is an HP engine it will be stamped HP there will be a date code for the assemble date and there may be other markings depending on oversized bearings, etc.
4. The above two examples will have had a service engine blue metal tag riveted to the side of the block. Over the years the tags were likely removed/lost but the the rivet hole will of course remain.
5. The other source for service engines came from left over factory ASSEMBLY plant inventory from the previous year after plant shut down for new model year change over. These engines were transferred to the parts depot warehouses to be used as "service engines" since they were already stamped with a model year code on the top pad and could not be used in the new model year cars. This is why there is a lot of confusion regarding the stampings of these engines and how they ended up in certain cars or when these engines surface WITHOUT a V.I.N. pad stamping. These engines would have been stamped (in the case of a 1969 model year 440) E440, they would have an assemble date code, an HP if it were and HP engine, other markings depending on oversized bearings etc., AND a blank V.I.N. pad as this engine was left over assembly plant stock that was never installed in a car. These engines may or may not have had the blue metal tags added to the block upon transfer to the parts warehouse but it is unlikely that they got them but never say never.
Then we have every senerio you can think of that happened to these engines AFTER they left Chrysler.
1. If one of these engines were being used as a warranty replacement, the dealership that installed it were instructed to stamp the V.I.N. pad with the car's V.I.N. however this seldom happened and if it did the mechanic that was stamping it would use whatever generic stamps that were available to him. So, 45 years later when all of the "numbers matching" gang start looking at these things , they often start pointing fingers saying "the owner restamped the block to make it a numbers matching car." As you can see, this may or may not be the case. Here are somev other examples of what COULD HAPPEN:
1. Lets say you had a 69 R/T with a 5 year/50,000 mile warranty and 2 years after you bought it, it throws a rod through the side of the block. The dealership gets approval for and orders a replacement engine. The one that they send just happens to be one of the left over engines from one of the assembly plants from the 69 model year. The casting date and assembly date are very close to the original engine in your car that blew up. The dealer installs the engine and may or may not stamp the V.I.N. on it. 30 years later a knowledgable Mopar buyer looks at the car when it is for sale. By this time the car has been through 10 different owners and no one knows the real story. If it was restamped by the dealership the buyer will likely suspect that one of the past owners restamped it because the characters don't look right.
2. If the V.I.N. pad is still blank does he think it is a factory error and they forgot to stamp it?
3. Does he look at this as an opportunity to explain to the owner that it does not have the original engine because it has no V.I.N. stamping?
4. Does he buy the car and then using the correct stamps turn it into "the original engine?"
5. The car over 30 years or less has been wrecked, rusted to the point that no one wants to drive it anymore and they junk it. Either they or the junk yard sells the engine. The V.I.N. pad was never stamped. Someone buys the engine and either they find a 1969 GTX or R/T car with a scheduled production date that lines up with the casting date and engine assembly date for this engine, or they advertise it and sell it to someone that has the appropriate car. They then stamp the virgin V.I.N. pad with THEIR V.I.N. and suddenly they have the "original engine" for their car.
If you think this is far fetch, I can tell you for a fact that it has been going on in the hobby (all makes) for as long as 35 years.
Consequently, there is a lot of value in the right engine to the right buyer.
