Your small gold coin from the German State of Hamburg contains 0.0576 troy ounces of pure gold. At approximately $930 US dollars per ounce at the time of this writing, the bullion value of your coin is 0.0576*930 = $54. You can look up the current value of gold on web sites such as kitco.com. Be sure to look it up. It changes every day.
But these are rare coins, so they are worth more than gold value alone. The catalogs say that only 400,000 were minted, and collectors love old gold coins. Not only that, 5 mark coins were minted in Hamburg exclusively in silver, except in 1877. Only during 1877 did Hamburg produce a 5 mark gold piece. These factors tend to push the value of your coin upward. Here are some typical catalog values:
average circulated: $350
well preserved: $400
fully uncirculated: $600
CoinQuest thanks Moneta Nova of Bremen for the picture of this gorgeous specimen. It is in such beautiful shape, the retail price is well over $1000. Nice coin!
One of our (ahem) better appraisals for gold coins like yours is found at this link. Click there to learn a little more.