Class that holds calculation results and has to be immutable
At the moment your class is not immutable because the Map given in the constructor is not copied (and Map itself isn't immutable). You should instead have a constructor like

public Result(final Map&lt;String, T&gt; result) {
    this.result = new LinkedHashMap&lt;&gt;(result);
}


What's the goal of the of() method ? Shouldn't it be named empty() instead ?

public static final Result&lt;Number&gt; empty() {
    return new Result&lt;&gt;(new LinkedHashMap&lt;&gt;());
}


Or having two parameters (1 key, 1 value) ?

public static final Result&lt;Number&gt; of(final String key, final T value) {
    Map&lt;String, T&gt; base = new LinkedHashMap&lt;&gt;();
    base.put(key, value);
    return new Result&lt;&gt;(base);
}


The fact that get() throws an IOException or a ClassNotFoundException bothers me because it makes the current underlying implementation "leaking" out of your class. Who wants (and expects) to have to handle an IOException when getting a value from a Map ?
Since these exceptions are not supposed to happen in this case, I would rethrow them as unchecked exceptions

@SuppressWarnings("unchecked")
public T get(final String key) throws Exception {
    try {
        return ((T) convertFromBytes(convertToBytes(result.get(key))));
    } 
    catch(IOException | ClassNotFoundException e) {
        throw new RuntimeException(e);
    }
}