Let's deal with the first cob. The second piece while hammered doesn't appear to be Spanish. My guess is that it is British. But back to your first piece in question.
It is an early Potosi piece (1617-1640). The use of roman numerals instead of arabic to denote the denomination and there is a faint trace of a date at 10 o'clock on the shield side. I can make out the x6xx. Dates didn't appear on Potosi cobs until 1617. So you have a 23 year window when your piece was minted. Most likely it was produced during the reign of King Philip IV. King Philip III reign came to end in the early years of the stated date range. Now, the assayer is in question. From my deciphering, there appears to be a faint vestige of the upper right bar of a "T". If that is accurate, then it would be Juan Ximenez de Tapia. The problem in nailing down a closer date range is that Juan served multiple terms.
With regards to the legend, it would "normally" read [Name of the King], BY THE GRACE OF GOD, KING OF SPAIN AND OF THE INDIES. It would start at 12 o'clock and proceed clockwise around the outer edge ending at 12 o'clock. So in your specific piece, it would read REX PHILIPVS IV, DEI GRATIA, REX HISPANIARVM ET INDIARVM. That would be the ideal phrasing, but nothing is ideal in these early pieces. There can be much variation. PHILIPVS IV or PHILIPVS IIII is possible. DEI GRATIA can be DEI G., DEI GRAT., or D.G. or just D. INDIARVM can be INDIAR., or IND., or even IN. Confused? Well sometimes the the first "I" in INDIARVM is rendered with a "Y". HISPANIARVM is often abbreviated as HISP. or HISPA. or HISPANI. and in some cases the letter "H" is omitted. During later periods there can be more identifiers in the legend, but that doesn't pertain to your piece.
What you see as "DV" is likely "PV" in philiPVs (I wrote in lowercase to emphasize the visible part that is in question). While it looks evident that it is a DV and not a PV, keep in mind that the "tail" of the "P" could be obscured with the comma-dot delimiter border.
Anyways, that is my WAG.
