Very cool finds! The antoninianus has to be Decius, although I am having trouble putting together the legend... it seems that the Abundantia type usually comes with a more robust legend, and the reverse doesn't seem like ABVNDANTIA AVG.
The Roman looks like Trajan Decius but I can not make sense of the legend. My coin with the IMP CAE TRA DECIVS AVG legend is overstruck on a Geta denarius and I have seen several other coins of the period somewhat garbled by being overstruck. Yours may be one???
The coin needs careful cleaning. At the top of the reverse, my imagination wants to read ALBINVS. Is this overstruck on Balbinus?
I feel like I can see CONS on obverse from 11:30-1 o'clock, and what appears initially to me as an O or Q at 3 o'clock but I think it's actually maybe a C with extreme serifs... Could this be a Consecration issue?? Could the lines in Decius' gave be striations from the wings of a left facing eagle or something?? Edit: or maybe IOVI CONSERVATORI??
Like @dougsmit said, the Reverse legend appears to read BALBINVSAV ?. After that bit of legend is another AVG in totally different style, makes sense what Doug said, overstruck on a Balbinus.
I actually think that is remnants of his Balbinus' cuirass. Edit: The both obv and rev legend size, spacing, slant appear to be similar (close to matching?) to this one: https://www.acsearch.info/search.html?id=499223
Thanks, guys.. Im completely lost..I will give this coin to my friend to be carefully cleaned under a microscope, so after cleaning up i will post photos...
I can't make out the ant very well but I think I see two O's in the inscription, so maybe Volusian. He used a legend C VIBIO VOLVSIANO on some coins. But the portrait looks a bit like Decius.
@paddyman98, @Treashunt, @galba68: take me along! I'll carry your gear, pack your lunch, wash your camel... Steve
Wonderful as usual, @galba68! Now that I'm soon to be (temporarily) unemployed, I'll have to try to get out detecting or fossil hunting soon.