Stamp Error: 1975 US Continental Army And Navy Uniforms

I have a sheet block with a line through the top row of stamps (1975 10 cent U.S. Continental Army and Navy Uniforms). At the time of purchase, I asked the PO clerk if other blocks had the line. He tried to reclaim them and was unable to find others. I doubt if others exist since the line fades somewhat towards the left side (as if sent through a press after a drop of ink spilled). (See photo) Does anyone have an idea how much something like this is worth?
Thanks

Hello....this is a very minor error, minimum value.

Surprisingly, printing anomalies such as this exist more often than we realize and secondary market values are not particularly high, although some will command a small premium. Further, because no two examples are exactly alike, there is no catalog or means to value each item individually. It comes down to what a buyer is willing to pay and what a seller is willing to accept for the item.

There are EFO (errors, freaks, oddities) collectors who may be interested in such an item, but many would prefer a perfect example rather than the smeared printing in the example shown.

Also, just for the record, the example shown is not considered an "error"; the smeared printing would be more properly identified as a "freak", as the smeared printing does not affect the postal use of the stamp since it was printed correctly, but merely shows some smeared ink, likely from a printing roller that was not cleaned properly.

I've used at least half a dozen of those PBs with inking smears for postage for that issue alone. It is not uncommon among the multi-colored stamp issues of that era. The 13c pottery issue is also notorious for having the inking smears run all the way across.

I imagine you can always find someone willing to pay a premium for them (or for anything).

Thanks everyone for your inputs! I suppose I'll just sit on it for another 18 years or until someone thinks it is special.