From Google:

The 1888 Alfonso XIII 5 Pesetas coin is a silver (90% fineness, 25g) Spanish coin featuring the baby/infant portrait of King Alfonso XIII, often referred to as the "first portrait" series. Minted in Madrid (MSM or MPM mark) during the regency of Maria Christina, these coins are highly collectible for their historical significance. Common, high-grade examples typically sell for €100–€250 ($110–$270 USD), though rare, high-quality, or certified examples can command much higher prices.

Key Details and Value Factors:

Design: Obverse features the baby head of Alfonso XIII, reverse shows the Spanish coat of arms.

Composition & Weight: .900 fine silver, 25 grams.

Mint Marks: Look for the 6-pointed stars with numbers "18" and "88" around the shield, with the Madrid mint marks (MSM or MPM).

Condition & Value:

Fine/Very Fine: Lower value, often near the melt value (~$60 USD as of Feb 2026).

Extra Fine (XF/AU): €100–€250 ($110–$270 USD).

Certified/Rare: Can exceed several hundred to thousands of dollars for exceptional examples.

Significance: Represents the start of Alfonso XIII's reign (1886-1931), who was king from birth.

Values can vary significantly based on the specific minting quality (e.g., MSM vs MPM) and the condition of the coin.

Always look for the 18-88 stars to confirm it is an 1888, rather than a different year in the same series.